I've never battled nor trained in a gym in Pokémon GO. I don't really know why; I think I've always felt intimidated and nervous to do so. I started playing last August (only a month after the game's release), but I there were so many people playing who seemed so advanced that I already felt behind. I decided that I would catch pokémon, build my collection and make it strong, and when I was strong enough, I would start battling.
I walked a lot, and I caught a lot. My collection grew, and I realized that the more pokémon I caught meant more and more resources (candies and star dust), and I could save those resources and really strengthen my collection. As I was approaching level 30, I decided to halt all evolutions and power-ups and catch every mon that crossed my path. My plan was to get to level 30, have a mass-evolution using my best baseline pokémon, then hit the gyms like a thunderstorm (Team Instinct obviously!).
That's just what I did- or just what I was doing. I was so close... so very close, but an unexpected obstacle threw everything off course. Two days before I finally reached level 30 was the major update which introduced gen 2 pokémon into the game. I felt absolutely defeated. I was so close to realizing my goal that had been six months in the making, and- BAM!- a slew of new pokémon that I knew nothing about (I never played past blue/red version of the main series games) appeared and complicated everything.
So, I just continued what I was doing now with even more monsters to catch. I still walk a lot and I still catch a lot, and I am following the same sort of guidelines I was following before terms of catching pookémon and building & strengthening may collection. I'm paying more attention to team leader appraisal of pokémon and battle move sets, and Im learning about the intricacies and idiosyncrasies of the gyms. And I'm leveling and evolving my pokémon using lucky eggs to maximize my experience points with the goal of gym battling in mind.
To date, I'm level 31 trainer with 1,484,925 star dust and loads of candies (>1400 Pidgey, >1200 Rattata, and >500 Sentret and Natu each). I've caught almost 5,500 pokémon and evolved nearly 550, and I am one hatchling shy of 700 eggs! I have some pretty strong pokémon, so I guess the question is... How/when do I get the courage to step into the gyn and prove to myself that I can battle with the rest of them?.