I have one on my forearm. They don't really hurt that bad and there wasn't much sensory overload to be had.
Of course, every autistic has their own issues with sensory, so I suppose it could vary. I'd just avoid the mid chest and ribcage for a first tattoo, your shoulder or forearm is a better place to start. In any case, if you're not sold on one you want, think about it for a few months. If you still want it, odds are you aren't going to regret it. I've had mine for a good 6 months now and I hold no regrets.
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If Jesus died for my sins, then I should sin as much as possible, so he didn't die for nothing.