As someone who solo q'ed to immo my best piece of advice is to get a duo ideally because its fucking miserable. If you can't find one just limit yourself to a certain amount of games per day (for me it was 3-4 even if im on a winstreak) and ONLY play 2 agents you're really good at
should also mention i did this last act hitting it for the first time so it's easily doable considering i hit it on smokes