EMPTY WALLET
This has been an enduring problem. But at least it's never been as acute as it was in the very beginning.
ACHING BACK
I remember it took maybe 3 full months of diving 1-2x a week before I stopped finding the weights and tank to be horribly heavy. I used to carry the tank & BCD to the water, then go back for the weight belt and put the BCD on in the water. I even asked a female-diver-also-doctor about buying some sort of back support, but she said to just give it a full 3-4 months and my muscles would probably build up to it. And that's exactly what happened. Now I'm over 50 and my 20-something son thinks mom's rig is HEAVY (make my day).
SORE ARCHES
My first 6 months or so, my feet used to ache after diving. I finally realized that I was unconciously clenching my foot as though I were trying to keep my foot inside an overlarge Crocs-shoe. Apparently I felt like my fins would otherwise fall off. It took me several months to get over this; I think it was more a matter of getting used to diving and relaxing in general than actually being able to consiously stop doing it.
BOUYANCY / TRIM
This is something you just get a completely different feel for once you dive regularly and have done it for some time. I remember when 1 kg more on one side than the other was an absolute catastrophe. Give it a little steady effort, then be patient and it will get better. It's like the chicken or the egg: you will probably find that as your bouyancy control improves, you need less weight, and as you carry less weight, your bouyancy control will improve; which change you notice first may vary.
GAS CONSUMPTION
Forgetaboutit. It is what it is; take a larger tank if you need one and tell yourself any higher consumption is 100% due to your excellent muscles. As you spend time on more important skills like bouyancy, trim, efficient kicks, no extranious movement (no windmilling hands, no unstoppably waving feet) and also just generally relax, better gas consumption might follow. If it doesn't, tell yourself you're just too excellent an athlete for improvement to be possible. Trying to improve you general level of fitness might help, but there again that's more likely to do all sorts of great things (feel better, look better, have more energy), but it may or may not affect you gas consumption. So forgetaboutit and work on the more guaranteed-return-for-effort items.