As someone with tattoos, I would just say..
"knock yourself out. Just put some thought into it, because it's going to be there forever. And be sure to look around for a good artist, that does the specific type of work you're looking at. Some people who do celtic key patterns really well might suck at portraits, for example, and it takes some looking to find the right artist to do exactly what you want. And when you find that artist, you're probably going to end up on a waiting list, and he quite possibly won't be local. When it finally comes time to get it, be sure to ask for and listen to any constructive ideas they have regarding your chosen design. They are the professionals, after all. And follow their advice for taking care of it. Since this is your first tattoo, it's going to feel like a bad sunburn for a while until it all heals up. If it's big enough they might have to do it in multiple sittings, like this one, that took 10 hours and two trips.
Hey... I think I'll get another one, too. Or another gun."
I like how you think, very rational and through!
(No purple in that line whatsoever!)