Hi there, welcome to the site. As far as starting your new aquarium I would recommend you read up on fishless cycling, which is a must before putting fish in a tank. Now a 44
gal is a good size to start with, but you will find a wide variety of results with DIY
CO2 for tanks that size. Usually above 29
gal people in the hobby prefer compressed
CO2, again that is up for debate, but just an issue to point out.
Other DIY proyects, do you have a hood and lights setup? You can always do that, guessing you will start with fresh water, so a sump is not really necesary, but since you have the skills you might attempt it for a future saltwater endevour. Ever heard of open bottom tanks? Look up my thread on setting one up, they might pick your fancy.