"free spirit" is "自由な精神" (jiyuu-na seishin). But, I guess that haveing 5 tatoo characters on your body may be a bit long. So, for this purpose, I may suggest "自由" (jiyuu: 'freedom') as an alternative.

For spirit I would use 魂　which is more 'soul' than 'spirit'.
The first may be simpler for a tattoo.

"Jiyuu-honpou" - "jiyuu" is freedom, "honpou" is "to behave as you feel, unfettered by the customs of society."

Together, they would mean something like: "freewheeling," or "Bohemian," but have the cooler feel of "free and easy."

It's alternative that refers more to a free-spirited, Bohemian, "On the Road" lifestyle or attitude.

It's clean, correct, aesthetically attractive, and even somewhat erudite. And hey, tattoo removal is a pain in the...

BTW, depending on your preferences, you might like 傍若無人 ("boujaku bujin"): "(behaving) as if nobody was around." This has both positive and negative connotations, though, so be careful. To overgeneralize, as I understand it "boujaku bujin" is a compliment in China and an insult in Japan.