Im a lvl 33 I can get up to 2 lvls a day while power leveling!
lvl 10s get to about lvl 23 in a day
lvl 20s to lvl 24s 25s to 28s and so on

All you have to do is open team search and look for preferably a lvl 50 tanker/scrapper and say "hi I was wondering if you wouldmind pling me"

if they say no go no to the next person till you find someone if your out of lvl 50s (tanker/scrapper) then go find someone 6-7 levels ahead of you (any higher than that you cannot get xp for the level 50s ill cover that next) that will give you good xp just not as much.

Now if you are wondering well if I team with a level 50 how do I get xp? well its really simple you also get a lvl 43 or 44 to join your team have them sidekick you and then have the lvl 50 to as many missions as possible results are assured! (before level 40 at least maybe after, there is no better way to get xp than this!