New here, profile advice and a few questions

Hi, I graduated in 2020 from a small unranked LAC. I studied pure math there and ended with a 3.82. I ended up in a FO (non-quantitative) role at a BB post graduation and have lately been looking a lot more into quantitative jobs/programs. I'd be looking to apply next cycle and would likely shoot for UChicago type schools. I have decent programming experience, having done projects/classes in Python and C++. I feel my profile is pretty strong overall, but plan to improve my programming skills prior to applying/starting any program. Will be studying for the GRE starting now, and feel quite confident I can end up with a good score.

The one thing I don't have is ODE, which judging by other threads, seems like something I will definitely need (the reason for this is that due to being pure I only needed x number of courses from a certain bucket of applied ones; I had a bad semester and ended up dropping ODE, but due to program requirements I did not ever end up having to take it again as I took another course to substitute). Any input as to whether I should just learn this on my own, or whether or not it will be a big enough gap such that not going ahead and taking it somewhere will significantly weaken my app? Additionally I would appreciate any other input as to how I can strengthen my profile between now and application time.