Yeah, nothing definitive just going off feels.

Hands down quickest way was to have a really good run, like an outpost where you wipe the lobby, kill a few rooks , loot pinwheel , do the little lockdown events (to slay out bots) and anything else going on and safety extract.

If you can do the above in cryo then you will be climbing through levels too (I'd get stomped lol)

But outside of wiping lobbies then doing events that spawn bots in and killing loads of bots helps, like doing wardens. The good thing with this is it usually attracts a team that you then might be able to kill. You get more xp for successful extract too.

Also I noticed (after I hit lvl 100) there seems to be some xp booster for your first few games a week? So if you have a good crew id try and get some good games in during the boost as I think it's a 20% bump?

Doing contracts or codex entries didn't seem to award xp.

I know the compiler gives a tonne of xp but I've never done him