So please no more input on "you should wait until your 25, or you need to think this through." I understand all that. I just wanted some ideas on what to get. . . .
I say this as a fellow with plenty of tattoos, who is married to a tattoo artist. Searching for the "right" tattoo is a process that takes a long time. And while there's nothing wrong with asking strangers for input, the decision on the artwork needs to come from your heart and soul. From your original post, it sounds like you're kind of wishy-washy on several different themes, which says to me that they don't really speak to your soul. You're doing the right thing in tossing out ideas and chewing on them, but the one you finally get should be the one that you decide you just can't live without. I know you're tired of all the advice on waiting and such, but I've seen a lot of people over the years get tattoos that weren't right for them, and they knew it.

So keep on playing the ideas through in your mind. One day it will come together and you'll know it's the right one.

The best thing to do, in my experience, is to scour the internet for images that you'd want to incorporate into the tattoo. Rough-sketch it out on paper, or copy/paste them in photoshop or something. Then take it to a reputable tattoo artist and ask them to sketch it up, resize it, etc. And be prepared to pay them for it. Nothing annoys a tattoo artist more than spending time sketching up random ideas for customers only to have them back out. But a good tattoo artist will be able to help you incorporate everything you want in the design and will probably give you realistic tips on what works well in ink and what doesn't. You'll definitely want that input from an experienced tattoo artist. Not everything that looks good on paper or on a computer screen will look good on skin. You'll need a tattoo artist to walk you through that so that your design is realistic for a tattoo.

Can't help with the Gaelic, sorry.

But on the clan badge, the unicorn might not be such a problem. I've noticed that clan badges tend to vary greatly in style; there seems to be plenty of room for artistic license. See if the tattoo artist can make the unicorn seem a little more bold or warrior-like instead of something that looks like it came from a child's cartoon book. A good artist can give the unicorn some muscling, make the horn look like a real weapon, and basically make it look like a horned war-horse.

Before picking a tattoo artist, make sure you look through all his photo books of past work. Definitely shop around and pick the guy (or gal) who you think is not only the best visual artist, but the best with the needle. I've seen tattoo artists that are masters at drawing on paper but just can't seem to make it work on skin. And vice-versa. So do your homework in picking an artist that can be creative with the design you want, as well as follow through when it comes to inking your skin.

And last but not least, don't EVER get a tattoo from the 'flash art' on the wall!