Rep ranges vary depending on a number of factors, including your experience and fitness level, as well as your goals and
training schedule. The number of reps suggested vary depending on if you're lifting for strength, building mass, leaning out, losing weight, building power, endurance, etc...
They're not etched in stone, and they have parameters.
Ideally after one or two warm up sets, your subsequent sets WILL bring you to muscle failure within that given set number (again depending on goal).
What are your goals?
Two exercises per major muscle group is usually sufficient.
I understand you're saying you cannot afford the gym membership, so you train once a week.... that needs to be encorporated into your goals as well so that you have realistic expectations of what you can achieve.
Question: What do you mean "it's crap" re: deadlifts at your gym? You just need a BB.
As for rep ranges, and a desire to build mass, it's important to understand periodizations so that you get yourself paced appropriately. You need to start on the first step and work your way through.
I honestly don't think you'll gain much mass lifting once per week, but I might be wrong,....it may have more to do with,...if you get yourself to a high enough
intensity level while you're there... if you don't get exhausted doing full body at that intensity....
I'm not sure.