Kinda annoyed I only found out about this just as I was about to leave university and only had time just to redownload the game. Looking to be able to find as close to the original 150 as I can and beat my original catch count of 85 Pokemon during the beta.
Since it was night time I was able to catch a lot of Zubat, so I could start getting it ready to evolve into a golbat (and then ended up catching one any way). I currently have 9 pokemon in my team and still siting on level four:
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Unfortunately not going out tomorrow, but will hopefully be catching more and taking over gyms on Friday.
You can't battle trainers in Pokemon GO. Only exception would be if a trainer left their Pokemon at a gym, and you'd have to battle that Pokemon there - but there is no PVP. Trading is something that is still to come in the future and has currently not been implemented yet.
PokeStops are only used to get items (pokeballs, revives, potions and eggs) and to attract pokemon with a Lure Module.