Regarding injection sites, I've always been told that it doesn't really matter where you inject, unless you are doing it incorrectly. It needs to be subcutaneous.
i've gotten glutathione, antibiotics, lidocaine, iv vitamins — all legit sources and worked as expected. stick with 1-2 vendors, the spam gets out of hand quick
Sharps disposal is worth setting up properly once the volume starts building - most pharmacies will take sealed sharps containers for free, and many states have mail-back programs for pharmaceutical waste. The household trash route with a sealed container works in a pinch but the pharmacy drop-off is the cleaner option for regular use.