You definetly need the first 4-5 perks for your alchemy skill tree. That will make your potions 80-%100 stronger. Your alchemy skill does not have to be 100. The potions that you create will turn your alchemy skill 100. Enchant a leather helmet, necklace, ring and bracers with fortify alchemy with the biggest soul gems you have. This is where a 100 enchanting skill comes in handy but it is not required. The lower your skills the more restoration potions you need to make, just dont enchant them too high or you will go into minus numbers.