"Can someone please recommend something that will consistently increase my scores?"
You are doing great. If there was some way to instantly inject a thick and robust history with long AAoA into the Fico/V3 algorithms, it would be easy, but it's not possible. Just keep adding green marks to your reports and get your limits up. I added about 22 accounts over a few years, took a year off, and made it the 800's (sometime my scores barely moved). Here's my 4 year history (Tax Lien still on TU).
and congrats on the build :]
I'm assuming you must have some lates on your report. I'm in a similar situation as you. My score went from the low 500's and now it's in the 640-670 range and not moving much. And that's because I have some late payments from 2 years ago.
Stop using Credit Karma to look at your credit score. The score they provide us only an entertainment score, not a score used by lenders. It isn't a good score for rebuilding purposes.
Get your FICO8 scores and use those instead.
The only other thing besides time moving your scores, is some one else's time.
The older the CC account the better. If a close family member has a CC that's say 10 yrs old or longer with perfect payment history/low utilization and the lender back dates for AUs. It will boost your scores as soon as it reports. I've helped more than one of my family members this way. It has never failed.
P.S. I know everyone is going to say “credit karma is not reliable...” but I am also using my FICO from AMEX that reports it hasn’t been changed. With the new card it reports 643EX. Before it hovered at 637. OHHHH, and my Credit One Card gives me access to my score and it said my EX was 660.
I'm not sure about Amex, but Credit Karma and Credit One do not provide Fico scores. Get your Fico scores to see your real progress.