If you're planning on getting serious about photography, get a copy of Adobe Lightroom now and learn it as you learn to take photos. Yes, there are plenty of free things out there, and yes, you can be a "serious photographer" and not use Lightroom. But it's quickly become the defacto standard foundation platform for the industry, and everything and anything else can be stacked on top of it, so there's a very strong chance you're going to wind up there eventually. LR5 can be had for around $75 if you look, and by the time the next release becomes necessary/desireable you may be ready to go subscription and add Photoshop to the bundle.
I've invested a lot of money in software in 3+ years of shooting, and Lightroom is the only piece I can't live without.