I don't recommend it. 5-HTP should never be used recreationaly I think. A year ago I was pretty depressive and decided to give a try to 5-htp. It did great for my depression after 2 weeks (I had also stopped smoking weed). But then I started smoking weed again, and therefore discovered that 5-htp made weed's high better. So I started taking 50-100 mg almost everytime I smoked. After a while 5-HTP seemed not to do anything anymore, weed's high had become dull, and my depressive state was back.
So 5-htp have many uses, but having fun is not one of them. It may help you sleep, help you recover from MDMA, even relax you, if taken regularly act as an effective anti-depressant, and even help you control your appetite, but don't use it to increase other drugs' effects or it will start messing with your sleep, energy, appetite and humor.