Hi and welcome to the forums!
Will your new Disco be your only open revolving account once it reports?
3 open revolvers and 1 installment is what is recommended for optimal scoring and rebuilding. I, personally, think it's best to get your first 3 cards around the same time so they can age together and build a solid foundation for your profile. After that - in the future - it's best practice to avoid sprees and space out your apps (tho few forum members follow this).
Any score drops due to a reduction in AAoA will return as the accounts age. You also may not incur any scoring penalties due to age if you don't pass below an age threshold for scoring. It all depends on your current profile.
What else is on your reports and what are the ages of your accounts (open and closed)? Also please note any negatives. If you can provide more profile-specific info, we can help you come up with a more personalized gameplan for building your credit.
There are different approaches with different pros and cons, so it depends not only on your profile, but on your goals. For example, do you plan to apply for a mortgage in the next year or two?
See my signature for one path, but, it's not for everybody.
In the long run, any method will work as long as it involves paying your bills on time 
Congrats on starting the journey and good luck!
@messy_hair wrote:Yes, it will be the only open revolving account once it begins reporting.
You should see a score increase once it reports -- FICO rewards you for opening your first revolver. Allow only a small balance -- around $5 or $10 dollars -- report to the bureaus. This will require you to pay your card down before the statement closing date as the creditor will report whatever your balance is on the date the statement closes. Then you'll need to pay the remaining balance due before the due date. Keeping the balance low will keep you from losing points for high utilization. Making sure the card has a balance the first time it reports will ensure you receive the max amount of bonus points for having an open account.
There are known scoring thresholds for revolving utilization - both individual and aggregate (there are slightly higher variations of these percentages that you may see in the forums - I use the ones provided below to be on the safe side and give room for any potential interest that may be applied to the balance).
Individual (card balance / card credit limit): 28.9%, 48.9%, 68.9%, 88.9%
You want to keep your individual card util below the 28.9% threshold whenever possible. Once you exceed 28.9%, you will be penalized. The higher the util, the worse the penalty.
Aggregate (combined total of all card balances / combined total of credit limit s ): 8.9%, 48.9%, 68.9%, 88.9%
Right now, your aggregate and individual util will be one and the same since you only have one card -- but once you have more than one card, your aggregate will be based on the combined total of balances / credit limits. You want to keep your aggregate below 8.9% for optimal scoring. You will be penalized for going above it, and, again, the higher the util, the worse the penalty. You'll see many places telling you that utilization below 30% is great -- and it's fine - the scoring penalty for being between 8.9% and 28.9% isn't too bad -- but you are losing out on ~12 points for being above 8.9% and less than 28.9%.
Since you'll only have one card, you will want to keep it's util below 8.9% of its credit limit since your aggregate and individual util will be the same.
Also note: never allow all cards to report a $0 balance. FICO also penalizes for having 'no revolving credit usage' so you need to have a balance report on at least one card at all times. This penalty is temporary though -- so in the event you have everything report $0, you'll lose 8-20 points (varies by profile) but those points will be regained the moment a card reports a balance.
@messy_hair wrote:
What is an age threshold of reporting?
As your accounts / overall credit profile ages, you get receive points as you pass above certain age thresholds and lose points when you fall back below them. For example, having your Average Age of Accounts (AAoA) reach the 2 year mark will result in a few point gains. Having your youngest revolving account (AoYRA) reach the one year mark will result in a few point gains. If your youngest revolver reaches one year and you gain some points and then you decide to app for a new card, you will lose the bonus points just gained because your AoYRA will be reset to 0 months. If your AAoA ages to 2 years and you receive your bonus points for that age, then go on an app spree that drops your AAoA to 1 year and 10 months, you will lose those bonus points you just gained for going over 2 years. Other aging metrics include your Age of Oldest Account (AoOA), Age of Youngest Account (AoYA) which includes all accounts, revolving and installments.
Inquiries can also be considered an aging metric --- you may have noticed that you tend to lose a few points whenever you incur a new inquiry. Any points lost when an inquiry is incurred are regained once the inquiry ages to 365 days -- the the inquiry will remain on your reports as a record for a full 2 years.
One thing to note is that account aging happens on the 1st of the month. So if you opened a card on Feb. 13th, that card will start its aging at 0 months as of Feb. 1st. It will be considered 1 month old on March 1st. If you check your scores on the 1st of the month and see an increase but no obvious reason as to why, it's most likely due to an aging factor. Inquiries, on the other hand, age by their exact date. So an inquiry from Feb. 13th will become unscoreable exactly 365 days from that date.
There are a ton of threads in the forum about aging metrics that you can read up on to learn how aging affects scoring and potential milestones you may want to look out for.
@messy_hair wrote:
I currently only have two accounts reporting on all three credit reports.
1. The closed credit card previously mentioned which was opened in 2012 and closed in fall of 2015. It is currently reporting 9 late payments.
Closed accounts will remain on your credit reports for ~10 years after the date of closure, during which time they will continue to age and factor into your age of accounts. This is currently your oldest account - when it drops off in 2025, you will likely see a bit of a decrease in score due to the loss in age since your next oldest will be the student loans opened in 2014.
When did the lates on this account occcur (month/year)? When the lates reach their 7 mark, they will begin to fall of your reports, eventually leaving you with a clean history on that account for the time it remains on your reports - something to look forward to.
@messy_hair wrote:
2. I have a 2 student loans. Both opened in 2014. I defaulted on the student loan back in 2019 and both are reporting closed. Both are reporting 13 late payments.
Are the loans now paid and just showing closed with some late payments? Or are they charged-off? Are these federal or private loans?
@messy_hair wrote:
I recently paid for removal on a collections and they removed it. My EQ jumped 30 points being 609 and TU jumped 14 to 614. Expierian is not reporting due to inactivity.
Nice! Congratulations on the removal and score increase! So EX hasn't been generating a score for you due to inactivity? If that's the case, it will take about 6 months after your Disco reports to generate a score.
@messy_hair wrote:My goal right now is to qualify for an FHA or USDA loan hopefully in the summer.
Have you pulled your mortgage scores yet (FICO 5, 4, 2)?
If your goal is to apply / obtain a mortgage, then we would normally advise not open any more credit at this time. It is recommended to not open any new accounts 12 months (at least) prior to obtaining a mortgage because mortgage scores are ultra sensitive to new accounts. You've already opened an account tho so this point is kinda moot.
I would probably advise you stick with the one card and just let it age, but others may advise you get 2 more cards asap and let the 3 age together. The reason for getting 3 cards now is because mortgage scores are also very sensitive to the number of cards reporting a balance -- it is best to have no more than 1/3 (33%) of your total cards report a balance for optimal scoring. It is impossible to meet that metric without having at least 3 revolving accounts. With only one card, you will always be at 100% of cards reporting a balance, with only 2 cards, you'll be, at best, 50%.... you need 3 cards to meet the 33% threshold.
I'm honestly not sure which would be more beneficial for you in the long run -- sticking with just the one card or getting 2 more now....
Is your timeframe for the summer set in stone?