I'm a harmonica(harp) player. Harmonicas are great starter interments. I can pick up a $5 C harp from a toy store and play an entire show with it. There are lots of tabs online for harp songs. You should learn how to play as many of them as you can. Sometimes people will be more impressed by your rendition of "Oh! Susanna." then they will be by the song you took forever to learn how to play. Also you simply can't be a harp playing and not know how to play "Oh! Susanna." Always keep your harp in your pocket and you can practice on the go. Although I would never suggest going through a break up your harp playing skill goes up drastically each breakup. So there's that!
Eventually you will need to buy a nice harmonica. For a full set(all 12 keys) of harmonicas you will spend around $300(comparable to most professional instruments), However you don't have to buy them all at once. $25 every fortnight for 6 months is cheap.(You probably won't even need all 12 keys) (Don't even consider USED harmonicas(You put them in your mouth)) As you get more harps try different more expensive brands. (I don't personally recommend brands that are nailed together. I tend to break these quickly)
Pushing the boundaries of what a harp is suppose to do is a huge part of getting better(tongue blocking, tongue slaps, growling, bends, overblown). That means that the better you get the more often you will break your harp. This just come with the territory of being good at playing a harp.
I'm very fond of using a cup to increase my harp resonance and vibrato.