Is It Worth Taking Classes Just for Recent Letters of Recommendation?

Hello I am new to the forum so hopefully this question hasn’t been asked before. I graduated in 2017, took some time off and am now preparing to apply to the 2021 cycle! I have kept in touch with one science professor but I don’t feel like I have a strong enough relationship with any other science or non-science professors. I do, however, have great letters from the managers where I worked the last two years but I know different schools have different requirements for LOR’s.

My BPCM/sGPA by year was 3.2 > 3.4 > 3.7 > 3.88 (cumulative 3.58) and my overall was 3.5 > 3.6 > 3.8 > 3.9 (cumulative 3.72). Although I am not super concerned about my grades thanks to the upward trend, should I consider taking post-bacc classes to give my GPA a little boost and make more recent relationships with professors who could write me a more personal Letter of Rec? Also if the classes I am taking are not pre-req’s, is it okay to take them at a community college?

Thank you so much! I love the podcast!!