Electronic gadgets to have handy

since i am a noob at electrical issues for atv's and other things i would like some advice on what to purchase to help me figure out my own problems. i want to learn but i will need gadgets to help. i have read about multi meters, 12v testers and etc... what exactly would i need to help figure out electrical issues? i have shop manual for my bike so thats a start.. also where can i get these gadgets and brands to stay clear from or brands that are approved by you folks, the experts?