Let me start by saying I'm sorry your marriage didn't work out as you'd hoped.
As for my experience, I wasn't a total casanova when I was young and single, and have been faithful to the woman I've married since getting involved with her a decade ago, but I had some good runs between relationships in my early 20s. There are still flirtations, and the immensely rare situation where a girl puts her energy out there for me to notice. But I'm happily married and appreciative for the spank material, as needed.
Anyhow, the "level up" concept is inherently flawed as it suggests that finding a less-inhibited FWB is simple to secure. Yes, those girls exist, but even then, frequency and quality are still byproducts of chemistry.
When I was younger, the one thing that was consistent with each positive experience was our personal chemistry being incredible. My confidence in my performance was always boosted by my comfort with the person. This is true with women, too. Nothing kills a sex drive like trying to match the energy (or lack thereof) of a bashful girl.
That doesn't mean every girl I had fun with was wife material or promiscuous, obviously. But I think it's important for inexperienced guys to understand the differences between a great sexual experience and a great experience with a great person that was also sexual. In the latter, we were confident discussing what we liked and didn't, and focused on pleasing one another. In the former, we applied the default move list:
You'll likely experience more of those, which will do nothing for your sexual confidence except confirm that you've just ejaculated. My confidence came from recognizing that the person was compatible, and not someone I had to convince that sex would be pretty okay with me.
Basically, if your first runs out there aren't producing results for your self-confidence, be sure to honestly assess the quality of the relationship. Ask: Do I really get along with her, or is there something mutually beneficial (but ultimately irrelevant) connecting us?
Anyhow, flex that mature "I'm divorced and have no time for the bullshit" muscle where you can. I hear it's an even stronger seduction tactic than being 28 with a good job and having your shit together.