U need a stable connection to play this game to avoid disconnection while having a league game. For newbies, It is recommended to use Terran and protoss since both of
these races are easier to micro compared to Zerg.

You need to know what is your basic units before playing a game such as do a research on your selected race first. What you need to do bow is focus only at 1 race. Once this is done, research on other races to see what units is able to anti which units.