As @skidoLLaZ and @gambleR mentioned, best thing to do is play a lot. Also, be sure to watch pro-streamers and tournaments. Half the time they explain their smokes, flashes, and ways to peak without being too overzealous.
For aim, join death match servers to help with your reaction and aiming abilities. Can go for either team DM’s or FFa’s, both help. One trick I use to do with my old team was everyone had to DM for at least 1 hour a day. I would set a goal of 50 M4a1 kills, 50 AK47 kills, 50 USP kills and 50 P250 kills; that way I had my rifle and pistol warm-up. Tweak to your meet your needs.
Game-sense comes with just playing a lot. You become aware of the common spots people tend to play, able to read a terrorist’s position from how the bomb is planted, where their smokes/mollys will most likely be placed, etc. Be sure to play with someone though, better to have at least one friend in game with you that you know will back you up as opposed to the constant baiters.