Dosage starting points?

I really wanna start DIY HRT, but

1, i dont know what dosages to use, Ive heard you should do a relatively low dose and then get bloodwork 1-2 months later, but what is considered the low dose? Im thinking about injections, how do i know when to increase and to what amounts?

2, ive searched it up and apparently you can take spironolactone with estrogen and progesterone together safely, is it reccomended when first doing DIY?

3, With the bloodwork, how often should i get tests and again, how should i know whats good/bad, and what to improve

4, what are reputable sources to get DiY hrt, ive been on https://hrtcafe.net/ to see sellers, should i buy the previous three from the same seller? or the cheapest but still trusted? idk, this is really stressful and confusing for me, but im tired of being on the waitlist.