When I first started getting in to producing, I thought that the big name programs were way too expensive, and spent a couple years puttering around with cheap programs before I figured everything out. Here's what I wish I had known:
-Music production isn't a free hobby. Nor is it cheap. Period.
-The most important thing to get at first is a DAW (digital audio workstation) like FL Studio, Reason, Ableton Live, Garage Band, etc. If you'd like, I can list more. Most of them are somewhat expensive. Generally, cheap or free programs are not going to be nearly as good as the more expensive ones.
Reaper is the primary exception to this and is the cheapest professional-quality DAW that I know of.
-Many of these DAWs have great free trials.
Here's FL Studio's and
here's Reason's.
-Every DAW is different (some more different than others), so play around and find the one you like the best. Don't limit yourself to my examples. Figure out what programs your favorite producers use and give those a shot.
-If you really can't afford the DAW you like, you can always get a cracked version. If you do this and end up sticking with the program, then I would suggest eventually buying it. Benefits of doing so include tech support, involvement in the community, and not being a prick to the developers who made the program you enjoy using.
-As an alternative to a DAW, you could try a tracker like
LMMS. Trackers tend to be free, which is cool, but they're kind of limited and different than the usual DAW. I've never used a tracker before so I'm no expert, but if you're intent on free software, invest some time in to researching them.
-Once you're set up with a program, Youtube tutorials are your friend. Playing around with the stuff you learned through video tutorials will help inspire dozens of songs. Never stop learning!
-Having some rudimentary piano skills helps immensely.
-There are some great production communities out there that are glad to answer your questions (clearly, you've already got this one). Continue asking them!