Help w/ farm

So I am nearing 30 and when on-level play pretty well...I normally stay in lane most of the time, except for beginning jungle and some blue grabs. When teammates back i cover and consequently get a decent amount of solo time in lane. For the first 15 mins or so, before anyone has a chance to really outlevel me, I normally go 3+ and 1...However, by about 20 I end up a few levels and 1-2k gold below everyone else and start getting rolled. I'm not sure where all this extra gold/xp is coming from and why I'm not getting it. Any suggestions?

It sounds like kill discrepancy, if you're not getting the last hit, your gold gains will suffer. Also, killing the jungle enemies yields a good amount of gold, you may need to branch out a bit more and kill some jungle creeps.

You could try midas boots if all else fails, but they're really bad boots compared to basically every other boot in the game.

Last hits, player kills, tower kills, fury farms and buff camps are all possible reasons. At later levels in the game when the lane-ing phase is braking down you should be able to clear out a fury farm or buff camp by yourself for some extra gold/xp. Just don't do so during a team fight, and make sure your jungler is either ok with it, or has outleveled the opposing team.