Xtol is sensitive to dissolved iron, so it's best mixed up from soft bottled drinking water - I use the 5L or 10L bag-in-box things and keep the Xtol in the bag once mixed up, which protects it from oxidation. It will keep for about a year like that. If you're shooting 135 and developing in inversion tanks, you'll use about 150mL of Xtol per film, so there's about 30 rolls of developer in a pack of Xtol.

Colour is harder because you need some temperature control at 38C, but certainly not impossible. My experience with C41 is that you can be pretty loose on the temperature and time and still get basically perfect results; it just changes the contrast. You have to make a major error (e.g. wrong pH due to incorrect mixing) to get bad colour, i.e. crossover.

PS if you're just starting out with development, you'd probably benefit from a flick through the FAQ in my signature.