I never regretted any of mine. I got one covered up because I liked another one more though. It was a small simple design so it worked out okay. Good, fool proof ones are like your astrology signs (obviously it won't change) or something that you are very passionate about. You also want to decide if you are going to do a larger piece or theme or a bunch of different ones. Once you do one you can't do the other. Be careful about anything that could be offensive, like a nake d woman. That can come back to bite you in the butt later.
The five I have are a kanji on the back of my neck, a large bound angel on my upper left arm, kanji that I got in japan with a design around it on my lower back, a dragon's eye with a tribal design on my upper back (it was my first and my biggest and it's about a foot in diameter) and my garbage pail kid on my right ribcage (that was the most painful. I would rather go through labor). I like all my tattoos. Yes they can be very expensive though. Find a good artist who is very clean. Make sure they sterilize everything. Look around the shop. Are there any gloves, ink, dirty towels or anything left out after they are done working?? Do they wipe everything down as soon as they are done? These are important things to know. After you get it done..........do not allow ANYONE to touch your tattoo. It is an open wound and can get infected easily. People have had limbs amputated because of infected tattoos. Also do not allow anyone to slap it. It causes the blood to come to the surface of the skin and can make your color bleed out. You just wasted a couple hundred dollars. Good luck on whatever you decide. Post pics.