Welcome!
The easy answer...get a amp.
The tricky part is explaining. Essentailly, the easier it is to get sound out of your setup the more likely you are to play. So flicking the 'on' switch on a amp is far easier than getting a audio interface based rig ready to rock.
I've tried to get a reliable PC based setup working - The temptation of free effects, amp sims, loopers, etc...got me hooked completely. Alas, it's finnicky and to get it reliable, it will actually cost $$$. And there's a fairly steep learning curve to getting it all to work... you'll need to go through a lot of home studio info to get familiar with the tools and techniques you'll need to get it working as a amp replacement. An exception to this *might* be an iPad + iRig + Amplitube - that was fairly straightforward to use
I do think a audio interface is a great tool and I'd get one - but for everyday ease of use while learning, a amp wins everytime.
Now....which amp? :roflmao:
Depends on what kinda music you be looking at making. If you have no preference, I just saw a Roland Cube 15 going for R500...no brainer at that price!
Here's a interesting thread to get you started :
http://www.guitarforum.co.za/guitar-gear/buying-your-first-gear-the-smart-way-the-singemonkey-approach/