Great game
I did find some glitches, like when you bought the aim point scope for the TMP, and placed it on the gun, you received the other one. And when you purchased the Glock 18 mod, it didn't work. But that's all I found.
After about 2 days of playing ( 3 hours) I got to wave 36. I found that the best pistol to start with was the Kimber, and then immediately attained the LAM; After I had the money I bought the silencer for it too. I then bought the TMP and the aimpoint sight when could afford it (even thought it appears as a different sight it will be useful later in the game), after that I bought the extended magazine. When I gained about 6500 I bought the AK-47, I bought all the modifications and slapped the aimpoint sight. With this setup I was able to take down technicals (with much practice) in one shot before they could stop. After buying the AK I bought 10 grenades, and found that this was a good amount to have at all times. Often times I would randomly chuck them while shooting enemies at a different spot. As soon as I could afford it I bought the M14. I bought all the modifications but the commando mod, this was the best setup I could but with any amount of money. After the next wave I bought the extra magazine vests and pouches. After this all my money was dedicated to buying C10s, grenades, and repairing the helicopter.
So in short my strategy was:
-KIMBER>TMP>AK-47>M14
-Repairing the helicopter comes first no matter what
- keep at least 10 grenades once you buy the AK
-target the RPGs first NO MATTER WHAT
-use grenades or shoot their gas tanks for the jeeps