I'll always get to GC/SKN/KN, which will net you an Assault class mech.
As far as how I play, I tend to play an assault role. I don't waste time hanging back with missiles, nor tagging. The extent of my tactics usually means using passive radar to close in for the kill, using jump jets to pop up, fire, and drop back behind cover, or stay just outside of a fight and pepper the enemies who are distracted by my teammates.
I favor mechs, and those that carry lasers, AC's, gauss, or PPCs. A typical progression for me is: I start with the pulse laser Uller, move to the beam laser Puma, go to the heavy gauss hollander, then its the gauss rifle demolisher, then the SSRM or 2 Cgauss Vulture. After that, I get a Madcat with gauss and beam lasers, followed by an Awesome with 6 beam lasers or 4PPCs. Next I'll get a Mauler with UACs or Gauss, and finish the round with the Mk2 (with gauss, lasers, and LRM10s or UACs) or an Atlas (with UACs or heavy gauss).
If all else fails, ask for donations. Players with extra c-bills are usually happy to contribute.
As you can see, my advice is different from the other two posters. Staying alive will help you to get more Cbills, but will slow rank progression since you'll be spending more time travelling back and forth and less fighting. My thinking is, if I'm a higher rank, I'll get the additional C-bills automatically from being that rank, rather than dying prematurely, and having to start with a smaller mech because I'm lower rank and can't afford the larger mech I was previously using.
Hope this helps.