need help with parlays and roundrobins..please hook it up

[ojsdaman]

whats up everyone... thanks in advance for the help.. i am somewhat new to sports betting although i have lost a ton in the past month.. i need someone to correct my thinking by either 1. showing me a website that gives strategys on what type of bets to make or 2. laying it down for me
This is what I have been doing... i have been betting on underdogs on the money line and then mixing them all up in parlays... with reading this forum i have read a bunch about parlays being -EV, but I am wondering why they are bad bets. also I am new to round robins and am wondering what is the best one to choose (if the round robins should be 2,3,or 4 team in each parlay)
Im sorry to bother you with all this but i dont know where to turn for answers and i love the games and have a great knowlege of sports but just need to be able to put it to use... thankyou very much for your time
Sincerely,
down$$