I have zero experience and have just been looking on Coinbase at the best and worst performers of the day.
I am thinking of buying coins that are 15% or more down and then selling once they pump 10% and move onto the next one that is 15% down and then again sell at 10% profit and just keep repeating.
Anyone done something similar or will it just lead me to losing my money?
As you newbie, don't be in a haste to start making money through trading, it takes time, there are many things you will have to learn, and you need time, if you are considering trading as a way for you to become rich over night, you will end up being frustrated and would at some point give up.
So if you want to succeed in trading, be patient and give yourself time, and also be consistent, do good research on every coin you want to buy and make sure your are only buying quality coins with good usecase, don't go buying dead coins with dead community, you will just end up making losses.