Best tip is to do the math calculation on how many candy's you'll need and how many you can evolve. So if you have like 100 pidgey's, then transfer 90 to get more candy. Then, get a rare egg for double xp - THEN evolve 10x pigey and you get like 5000xp each time or something like that..... Cuz some you can only evolve once..
As your character level increases, so does the CP of what you find. I've slowly begun finding now 200+'s, I got a 200 pikachu and such in downtown today.
But going outside is all the fun. I don't think it would be as fun sitting inside .. it's the entire point. Going out with some people and walking around. Just on my lunch break went over to startbucks - 6 other people I walked into playing and they all chatted me up and said "what did you get from this pokestop" lol... no joke..
The gym's I've seen have had some level 600's and such. There's guy on Reddit who are level 25 and find level 1,800CP pokemon's and they're doing it fully legit! (The tip above is mentioned for evolving is the absolute best).