your sense/dpi will start off high but id recommend slowly moving it down when you feel like you're not hitting as many shots as you think you can (tracer/genji tend to do better with higher DPI but it's all personal preference), lots of practice range/ana easy bots in custom + deathmatch/QP
Dont do ranked when you hit lvl 25 you may have game sense but it takes ages to get good with mouse, i made the mistake, now im stuck in gold when i have the skill to take of high plat low diamonds