There are a ton of really good semi-pro magazines that pay nothing, but might give you good experience. There is a third tier of semi-pro magazines that pay very little, but may give you good experience, good editing and a bit of exposure. There is a second tier of semi-pro magazines that pay somewhat more, give you good experience and editing, and a good bit more exposure. And lastly there are the pro magazines, which are pros because they pay the going pro rates, and obviously they are going to give you the most exposure. Sorting through them becomes a matter of monitoring the market, of learning who the publications are, how often their names come up in the field, how well known they are, who the editors are, etc.
How much time you want to put into that is up to you. But it really doesn't hurt to start with submissions to the pro mags and work your way down the rate scale, keeping in mind what sort of stories in general a particular mag is after. It can take a long time to get a sale and magazines go out of business every five seconds, but it's not bad training for the book market, or if you just want to do shorts. It's a good lesson in persistence.