I don't believe in applying the "law" here and there's no condemnation for having or getting tattoos.
The context of the OT passage about marking yourself had a specific application among a specific people. You're almost certainly NOT in that group with that motive.
My personal opinion, is that a tattoo can not exceed the beauty God gave the human body. I realize that people do not take care of themselves and are over/under weight, and avail themselves of the worldly culture, which they should be apart from as new creations, but you can get one and still be a believer.
As a man, you can show me pretty much any tattoo and put it on a woman, and it will NOT enhance or exceed her personal beauty. In many cases, it ADVERSELY detracts from her appearance. Some might consider it more manly to put a symbol on a (man's) body, even "tastefully", but take a poll of most people who can give their honest opinion (not in the hearing of the wearer) and probably the majority of those polled will say that they looked better the way God made them in the first place.
People "support" others in what they do?! "How do you like my tattoo?" "Oh yeah!" But inside they're going, "I would NEVER have done that". But they're supportive of this, or a hair style and so... whatever!
As believers people shouldn't really make an idol of their own flesh. Everything you project should be of God and His kingdom (not your flesh). If you want to promote God or His kingdom, that's better. You can do that wearing shirts, jewelry, etc. just as well. It's true maybe a Godly tattoo might reach an ungodly person wearing a tattoo, but be prayerful about what you do to your body.
Your audience (whom you don't know down the road who God will place you among) might be offended by your "ink". You might have to wear long sleeve shirts in the company of some folks so you don't lose them in the natural and obscure your witness.
If a woman took a poll about a certain tattoo she thought about getting, and nobody knew who it was and could receive honest feedback, especially from men, she'd probably find that her own God given beauty well exceeded her plans for some (typically) green ink that will fade and become somewhat misshaped over time as your body shape changes. Guess what? You looked better before and the man you might end up with secretly prefers you didn't have the tattoo!
You can get temporary tattoos that you design and print. Try them on. You can actually change your message, which you CAN"T do after you commit yourself.
"Nothin's sure but this brand new tatoo." (A lifelong choice you made when you were prone to make bad choices.)