noob Z player needs help


im new to SC2 and im in the bronze league.

i'v been watching some of day 9 videos and some other players replay i see them droning all the time..

i keep dronning all the time and try to keep my minerals on less then 500 but in some point i can't do it i get to huge amounts of minerals using only 3 bases i know this is not good and its making me lose alot..

after i get my 3rd and my opponent haven't attacked me i start getting some units just to waste my minerals but i keep getting my ass kicked all the time 

i go for 14 hatch 15 pool 16 gas with 2 queens and 2 evos i don't know what i am doing wrong...

if please anyone can help me i'll be grateful thank in advance : )