>>I am slowly going to be purchasing the supplies I will need for a collared lizard or two, and then the lizards themselves.
Congratulations on being smarter than a large segment of the population which "does it backwards" (gets the lizards first, then asks "what do they eat?" etc.). 
>>1. I want a more than "minimum" enclosure. So I am shooting for a 60-90 gallon. What are your thoughts on enclosure size?
If you can, restrict your activity to your kitchen pantry and let the lizards have the rest of the house! Seriously, bigger is always better. Keep in mind that your limiting factor will likely be the doorway of the room in which you intend to keep the lizards, as well as the hallways leading into it (for example, if you must maneuver around a tight corner). I'm speaking from experience: I like designing my own enclosures, and I had a LOT of trouble with one or two--you build it perfect, then you can't get it into the room!
2. Are both aquariums and custom made melamine (with needed airflow installed of course) both appropriate options?
When I think melamine, I think of that particle board stuff coated with a water-resistant coating. First of all, it's HEAVY, and second, if water gets through to the particle board (such as through a cut surface), the particle board will disintegrate into...particles. Glass can be relatively heavy, too, but it's more scratch-resistant than lighter alternatives like acrylic.
I've had enclosures constructed of plywood coated with polyurethane for a nontoxic, waterproof surface, with the front made of a pane of glass. Depending on the size of the enclosure, it can get heavy, but I had to make do with the basic frame which someone else "overbuilt" (too thick plywood)--with proper design, you can use fairly thin plywood (it's not like the collareds are going to "bust out" like a Nile monitor!).
>>3. Are crickets the main staple most people feed?
Seems that way. I don't currently have any collareds, so I'll let the other folks answer this one!
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Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet