What is the best product for split ends and breakage?

You won't find anything to repair your hair and the only way to get rid of them is to get them trimmed off. Until then, deep condition your hair once maybe twice a week, depending on the damage to prevent the rest of the length of hair from splitting. Use heat protection spray to minimise the damage caused by heat styling too and try not to overdye it if you dye it normally.
Tigi do a great finishing product called ego boost which deals with fly aways and temporarily seals the splits so they don't look so obvious but the prevention is always better than a cure, deep condition once a week after you get the dead ends chopped off and damage shouldn't be so bad in the future.