It's really common for new people to leap into making some huge epic series, thinking "this is gonna be the big one! This will be my magnum opus!" and then you only get a few strips in before you come across every newbie problem, and you learn to fix them, but now the old pages look like crap compared to the newer ones and...aaagh. So making short comics is the best way to go.
Short comics, you have to really think about setup-climax-ending and pace out your pages to a specific count, you can't just start and see where it goes, so they will teach you a lot about pacing. Plus you get to test run ideas, see what elements of your work the audience reacts to, and what type of comics people like from you.
Finally, you're not pinned to one genre or story. If you're overflowing with ideas, this is so great. Posting individual pages, some of my short comics in the past have included:
A hopeful, lighthearted story set in a dystopian sci-fi world drawn in very stark, blocky black and white:
A very fluffy shoujo manga inspired romance about a message in a bottle causing two bored teenagers on the beach to meet.
A comic for kids about accepting people who are different.
If I'd been chained to one comic I couldn't have tried these things out, or done these little style tests to find ideas to take to my longer comics.
My other advice is, you can always write an idea down for later. Some ideas are really cool, but aren't enough to support a whole comic on their own, so sometimes I stick ideas together like lego bricks to create something bigger. Like "hmm, I like these characters from this idea, but the rest of it kinda sucks, so I'm going to keep them but put them into another story..." (this is actually what happened with Rekki and Subo in Errant. They were originally guard characters for a spoiled prince in a sort of....isekai-ish story about girls from our world who find a portal to a magical world in the woods. I kept the runic magic, the square-shaped swords, Rekki and Subo and... dumped like everything else from that).