This is what I do: Buy a Raven B. Go out and locate the enemy and utilize your C3 to transmit the data to your allies. You will begin gaining C-bills just for having them in range. Additionally, you have an ELRM-15. Find the enemy missile boats (usually cougars with 4 LRM-10s) Bomb on them beyond the range of their radar and weapons. Cause them to run around like mad looking for you. Use your Machine Guns on any enemy BA, VTOLs, or Aerospace. If you can manage consistent hits with your LRMs you will probably have nabbed a kill or two.
You can then return to base, sell your completely undamaged Raven B and use the cash you've accumulated to buy a bigger mech. I don't usually do this because I'm the type of player who wants to make sure his team is as strong as possible, so I will generally dole out cash to guys like you who need to get into a bigger machine before they can start wrecking the enemy. I'm totally cool with that. I generally stay in a Raven B for about 15-20 minutes on a normal 45 minute match. I take it back to hangar about 3 times, and on the 3rd is when I usually upgrade to a Catapult Prime, or, if I have the cash, I get into the Warhammer Prime. If I don't have the cash, I usually find that the guys I helped get into heavy mechs earlier are more than happy to kick some cash my way.