It really would help if we knew your FICO scores, or at least a few of them from the various bureaus and CRAs
That said.. gardening is as easy as just saying NO to apping for new products or CLIs or opening new lines of credit .... Basically NO HPs.. (Hard Pulls)....
Even knowing as little as I do because this is one of those things thats more score dependant (and HP dependant)... The primary purpose of gardening is to let your cards grow, become paid down and off, and let your hard pulls age.....
A good start is as you said... wait untill stuff is paid off, then examine your scores and pulls... But even without that.. id start off with 6 months, then perhaps extending it out in multiples of 6 months...
Its really about time passing and things falling off... and HPs falling off and being aged along with increasing the age of the accounts you do have....
Join us in the garden thread to pass the time, and pick up some hints and suggestions..
-J
Congratulations on your new home! That’s great. Regarding gardening, we don’t really know enough to answer your question. Technically you could garden forever lol, so the question is what are you gardening for? Also, we don’t know the ages of any of your non-recent accounts, average age or oldest. You’ve taken on quite a lot recently so gardening for at least a year or two is probably recommended but where do you want to go from here? Higher limit cards? Opening too many things at the same time means you risk getting low limits and denials.
As others have said, gardening is simply not doing anything that will cause hard pulls (inquiries) on your report, or opening new tradelines, for a period of time.
The purposes of gardening are to:
1. Let your accounts age ("grow"). New accounts ("seedlings") cause score dings, and too many over a short time can lead to denials. As they grow (age) and you make payments on time your score will improve.
2. Let inquiries age and fall off. Inquiries (hard pulls) cause score drops, and like new accounts, too many can lead to denials/AA. These drops recover over time and after 1 year, the inquiry no longer impacts your FICO score, and after 2 years, disappears from your reports entirely.
3. Gives you time to pay down balances, which will also improve your scores.
4. Gives derogatory items (deliquencies, late payments etc) time to age and eventually fall off.
How long to garden? That depends on your goals and your particular credit profile.
1. You might have a goal down the road that requires optimal credit, such as buying a home or a car. You would want to garden in the months leading up to this purchase so your scores are best suited for a mortgage approval and a good rate.
2. You might have high utilization or debt, and need time to pay it down.
3. Maybe you want a new Chase card but are over 5/24, and need to garden until you have fewer than 5 new accounts in 24 months.
4. You want your scores to grow, for any reason.
5. You have derogatories or are rebuilding, and after getting your needed mix of accounts to start, you want to garden for a while and let those accounts age and the inquiries to drop off, or even for the derogs to age or drop off.
6. Or maybe you're happy with what you have, and simply don't need new credit. Anytime you aren't apping or taking hard pulls, you're gardening, whether you know it or not. 
I did it for 8 years once, though I hadn't heard of "gardening". I just had no need to apply for anything.
6 months is a good minimum between apps to let accounts age and reduce the chance of a denial. 2 years is also a great gardening goal, as inquiries drop off after 2 years, and you'd wind up at 0/24 for a future Chase app. If you want to go longer, you can, it never hurts. Older accounts in good standing result in higher and more stable scores than a large number of newer acconts. (AAoA, Average Age of Accounts) is an important metric that gardening will allow to grow.
