As said, if you want a team, join an existing faction. Established factions know how to avoid spies/infiltrators. If you start your own, it will be destroyed by other players. (This game's player count is far too low to recruit and build a new team - the infiltrator ratio is very high right now.) As FireFlare said, being on a team makes things much easier (and often funner). They know how to do things that might take an average player months [and months] to discover. Ways to power-level included.
Power Leveling Methods In Use Now
Classic: hunt centaurs, floaters, and aliens in desert. Encounter after encounter.
Junk: (warning, this might be cheating) gather junk for hours and hours, craft certain items, upgrade certain pistols, dismantle them and upgrade them again. (Or something like that. I don't know because i never did this.)
Caravans: the amount of xp you get from caravans scales up as you level up.