Houmous is just chickpeas cooked and then smoothified (ahem)!
I think you can add other stuff too it like lemon juice etc but I would try just doing the chickpeas and then adding whichever ingredient you think goes. Chickpeas are quite cheap to buy and they're free!
You would usually use tahini but that has oil in it so would be synned. Free houmus is a tin of chick peas, lemon juice, garlic and you can add some natural yoghurt to loosen it a bit. You would usually use olive oil but obviously thats synned too.