The definition of addiction, as I understand it, is becoming physically dependent on something to the point where you go through withdrawal when you stop. This just isn't possible with mj.
The risk is that you enjoy so much that you use in inappropriately. This has a bit to do with your tolerance and the potency of the herb. It's going to be a learning process. Fortunately if you use a dispensary you'll have a good idea of the strength indicated in milligrams. If you only had two hits and you couldn't think strait for an hour, you'll know to get weaker stuff or just have one hit. If you take a bit too much you'll either pass out for a few hours or have anxiety, neither of which are terrible.
The other advantage of dispensaries is that you know quite a bit about what you're getting and after trying a few kinds you'll have an idea of whether you want a sativa or indica dominant hybrid. Most people like sativa dominant hybrids the most so that's the majority of what you'll find. It's nice to have a little bit of an indica dominant around as a nice nightcap though.
Many people do not get high on their first try so do it a couple times before making any strict judgement calls.
Once you get comfortable with small doses you can start experimenting with stronger strains and unlocking some of the more psychedelic effects that are a lot of fun.