you're on a good start, especially for someone who had nothing to go on but pet store advice. a few pointers though:
- 1.5 gallons may very well be big enough for him, but if he looks bored or overly lazy, you might want to upgrade him to a 3-5 gallon tank so he has some more swimming room.
- you're gonna need a heater. for an under 5 gallon tank that shouldn't run you any more than $12-15. if you can't find one that'll work for your volume with an adjuster knob, you can hook it up to a dimmer switch and adjust the temperature that way.
-make sure your plants are silk or another fabric, not plastic. especially for heavy-finned breeds like halfmoons, plastic plants can be dangerous since they can tear their delicate fins, which, in addition to being unsightly, can lead to infections for your little guy.
-glofish gravel doesn't glow in the dark, it glows under blue-spectrum LED lights.
other than that, welcome to the wonderful world of betta addiction.