If you're planning on playing anything longer than past level 20, it's not worth it if you don't buy premium. You'll always be at a disadvantage in PvP. It's also not that expensive, considering a single civ is like R150, and games generally cost around R400 nowadays.
The way civ work is that they can be compared to being characters in WoW. Imagine getting WoW for free, but then just paying R150 for a character. Except the characters are more or less balanced in a way that they're all almost the same.