If you are handy and build things well, making a forge is pretty simple. There is all sorts of info in the stickys.
However, if you want to forge knives instead of build forges, a small commercial forge is a good alternative. Check out the Atlas forges. They are made by one of the BF guys here. They are great for the beginning forger. If/when you outgrow it, it will still have a place in the shop, and you can build/buy a larger forge for things like making damascus and big knives.