Arcylic tanks are REALLY easy to make. Ive made a few of them from 10 to 50 gallons. Make sure you get the right kind of weldon for what you want to make. 3 and 4 are great but watery. 16 is good for filling gaps or if youre new to acrylic.
Glass tanks are not really any harder, just different and its really hard to get glass at a low enough price to make it worth while. Ive found unless its a large custom size tank its usually cheaper to buy a glass tank than make it.
Someone on here with good experience building acrylic tanks should hold a workshop somewhere. I'd be down to attend it. I think I want to build my own tank and sump.