You don't need any post processing software to take decent pictures and I certainly wouldn't advise it if your not very confident, I think it will just wind you up.
Most computers now come with photo editing software, get to grips and understand what can be done in those programs first before shelling out for Lightroom or Photoshop. These will allow you to crop, edit the contrast, brightness and colour.
Some may tell you these are rubbish and you can only edit pictures with the file extention .jpg but as a starting point it's free and you get to practice enhancing your pictures.
This is exactly what I used to do up until a few weeks ago, I'm now struggling to get to grips with editing RAW images and I get very tempted just to go back to post processing .jpg.
In my experience if you start posting images and asking for criticism you will begin to learn a lot more. Obviously some criticism is to personal taste but a lot more of it can be very helpful, especially if you ask.