The problem with herbal based testosterone boosters like tongcat ali is that they don't do much by themselves. You really need to stack a couple good natural herbal based testosterone boosters together in order to really notice anything from them.
Rather then just use a tongcat ali supplement, I would use a multi-ingredient herbal based testosterone booster like HCGenerate from n2bm.com. It'll be a little bit more expensive but it will be much more effective.
It's kind of like going to the gym for a workout. You wouldn't just want to do one exercise. You would want to do multiple exercises to get the best bang for your buck.