You can go plywood if you want to build. Lots of thread and stronger and longer lasting than any other tank. That is an option depending on your skill level with tools, wood, etc.
You can go custom. Several to choose from. Higher cost. Longer lead time in some cases. However, you get what you want and can build some extra strength such as upper and lower bracing and in some cases even sides.
Glass or acrylic both have pro and cons. I believe it is a personal preference but having owned both my take is larger glass tanks require more logistics to move. Not only move but if you decide to move be it selling or buying new home or even just wanting to move tank location glass is a big effort. Larger tank, thicker glass, etc. I recently upgraded to a 210 gallon glass tank and sort of kicking my self in the rear since it was difficult to man handle. Yes, acrylic scratches but as said above you can buff - just takes time, or money, to have it done.
What is the right size to get back in? Personal preference. What sort of space do you have first to work with. After that what is your budget. Budget needs to include most things and the larger tank means larger supporting equipment. Total sum of all compare to your budget and you have your answer. I'm talking larger tanks mean larger return pumps. Return pumps can be single, ok, but also redundant, better. You need more water. More salt. More power heads. Power heads mean clutter so do you want closed loop to declutter. More substrate, more rock. Live rock, or dry?
For me, personally, start toying around with size, estimated tank cost, stand cost, and some supporting equipment like lighting, skimmer, sump, rocks, salt mix, substrate, heaters, pumps, and power heads. Look at that number and go from there. I think you will get an idea of a tank size range to work within your budget. I'm betting 180 to 320 gallons depending if you buy a pre-built tank or custom.
