It all depends on whether you prefer speed over quantity - or both
You can easily do 60GB/month on 384kbps Mweb uncapped.
If you know that you're going to use less than 30GB/month, then I'd suggest looking at capped accounts first - because there are lots of different packages and configurations to choose from.
You can cut your costs considerably by using (Internet Solutions') local only accounts, but then you should look at splitting traffic between local & international accounts.
If you set up your routing & DNS correctly, then you can download most of the YouTube, Google, Facebook, Microsoft, Nvidia & AMD content via the local only account. You also get local DC++ & Usenet/NNTP servers, from which you can download like series.
Like I'm currently using 10GB+40GB IS local only accounts (~R200pm) for local & international stuff + 1GB Afrihost (free) account for when my IS local accounts lose their international cap + 1GB WebAfrica prepaid account (R15 once off) for WAGE stuff OR when all the other accounts' caps are depleted.
You can use like a MikroTik RB750 (under R400 incl VAT) to do the splitting for you, which I'll recommend if you have multiple PC's/network devices. You can split even the traffic of wireless devices in a setup where you have an ADSL modem (that also acts as an WiFi AP) and then the RB750 connected to it via LAN cable. If you don't want to split the traffic on a dedicated router like the RB750, then you can use an application like my Traffic Splitter to route the traffic for you, but then you'll have to run that application on each and every PC where you want to split the traffic.
Unfortunately splitting traffic requires an ADSL modem that supports bridge mode, which like the Netgear DGN2200 doesn't have. This is just one of the many reasons why I'd suggest D-Link & TP-Link ADSL modems above Netgear ones.
@venom: you can get about 65GB from 2x 30GB is local only accounts, which would set you back R250, and then you can download at 10Mbps speeds.
Then there are also the exploit that as long as you keep the PPPoE connection to the IS local only account connected, which requires a very stable ADSL connection, then you get to keep your international connectivity, and not just the small 2GB blended part of the 30GB local only account.