Oh man, I'll gladly accept any White Collar recs you have :D :D
Well well WELL. So my bookmarks are generally kind of lacking and surprisingly G-rated from what I remember that reading spree to be like, but to start you off:
watch this delightful OT3 vid by china_shop where Elizabeth Burke gets all she deserves and everyone is attractive
Martyrs Never Last This Long by out_there is Peter/Neal and Peter/Neal/El and it’s Mozzie POV which is 100% fantastic. It's early-season and lighthearted and basically exactly what I go to White Collar for: Mozzie’s righteous exasperation.
World Tour by cherryfeather is the fic that made me an OT3 shipper, because I was having all these “idk... but... consent...?” kind of feelings about Peter/Neal and this side-steps it by being a future-fic and very much in keeping with the characters and style of the show.
The Right Way to Fall by Sholio is the guardian angel AU that I mentioned in tags because I love it so much. Sholio is a prolific White Collar author -- not a lot of porn and mostly canon pairings or gen, but if you’re into episode-related fic, wacky AUs, and h/c tropes, take a look through their catalog.
Beautiful Perfect Good by OnYourMark is quality OT3 goodness and I don’t remember much about it but it’s E-rated and everything else I’ve given you is just way too pure, so hit this up :)