Pokemon-go – Does leveling up increase your range

Like Samthere said, you can delay indefinitely, however id recommend keeping one Pokemon high to take gyms with. Don't power it up more than you have to but keep it high enough to get at least a few gyms. The extra star dust and coins you get should be worth the candies and stardust you spend to keep just one Pokemon high. I usually get rid of anything with a CP meter under 90%. It's probably good to set a goal like level 25, otherwise you probably will delay it indefinitely. Lastly, go ahead and evolve any Ratatas and Spearows (or other really common ones in your area) you can for the experience. Their evolved forms max out pretty low so they aren't really viable later, otherwise leveling will get really slow unless you are hatching eggs left and right.

Getting a Throw Bonus will increase your chances of getting a Pokemon, with an Excellent Throw resulting in a rather sharp spike to catch chances.

However, to get the XP bonus (and the catchrate bonus), you actually have to hit inside the shrinking circle. It isn't enough to wait for the circle to become small, you must still hit inside the circle and get the bonus.

You can also take your time throwing: the circle will expand out after hitting its smallest point.