I need a knives expert!!!?

i'm planing on purchasing a knife. i am an unofficial "weapons expert", enough to know there is a big difference between a war/battle worthy blade like a sword, and a tool/gardening blade like a machete. but i don't really know that much out of knifes, so i need a knives expert to suggest me a good knife for self defense, a good brand and model (not too pricey if possible). if it's not too much to ask, plz leave multiple models and suggestions. thank you.