I downloaded this about three weeks ago now. I initially got it because the week before I installed a life log app so we could see how much walking we did when we're out, as we're on a bit of "let's stop being such fatties" kick and I thought playing Pokemon and hatching eggs would encourage us to actually go out and do it.
Currently I'm sat at mid level 21, around level 16 I started becoming really interested in playing it as a game for rewards and xp and stuff so it definitely got more addictive for me the more I played. We'll set an egg hatching goal before we leave the house so generally we'll walk at least 5k a night. I pissed away a fair bit of Stardust in the earlier levels, thinking that at level 5 when I could join a gym, I would do that straight away but then I did a bit of looking into it, checking IV values etc. and levelled no Pokemon up until I got to level 20. Got from level 17 to 20 in one evening due to a lucky eggs and doing a big multi evolve. I also got lucky and hatched a Snorlax the same night, which was itself level 20, he's now maxed out at 1978 but I'll keep bumping him up with me when I level up. He doesn't have the best moveset in the world but I don't fancy my chance of coming across a better one anytime soon. I did get a little impatient with evolving my Vaporeon, who I've renamed Fishcakes, as although he's got good potential (86%) he's currently only at level 16.5. So I sort of wish I'd waited to catch a better one at level 20+ before evolving him. I think my next Eevee will be a Flareon, and then I'll just roll the dice on the rest and hope for a better Vaporeon.
Got my last 9 Magikarp for a Gyarados last night too! He's cool. I'm now only pumping Stardust into Pokemon that have IV values higher than 85% so I'm finding waiting until I caught better ones before levelling up has paid off. Also caught a Dragonair last night, which exhausted my Ultra ball stock. Totally worth it though because he's a level 22.5 and is 86.7% perfect
He'll make a kick-ass Dragonite, if I ever find enough Dratini.... Had a go at training at friendly gym last night for the first time, I had no idea what I was doing. Or why. Or how to join as opposed to just train. Or how to use a different Pokemon. But I looked online last night and feel a bit more confident for my next attempt.
I'm finding getting the bloody things to stay in the ball more tricky now, even ones with <100cp. I'm not good enough at catching to fire a curve ball and land a great or excellent throw every time so I'm having to be a bit more selective over which ones I catch at times.