Is there a list anywhere of all the best spells to get? Like longest soultrap spell and strongest fire damage spell etc.

There is a spell list, check the Forum Links Directory(FLD) at the top of the forum list.

I believe there is a comprehensive list of spells and who sells them on the Unofficial Elder Scrolls Pages(UESP.com) as well.

Fact is, after you know a given type of spell(i.e. restore health, restore fatigue, fire damage, soultrap, fortify ability, etc.), you can visit a Spellmaker and have a custom spell of that type made.

For example: after you buy Jack of All Trades(Fortify Luck) from Arille's Tradehouse(sold by Arille) in Seyda Neen(the starting town), you can visit the Balmora Mages Guild and have one of the mages there create a Fortify Strength spell limited only by the amount of cash you have to buy it, and name it anything you like.

There are only a few rare spell types that are only available in some remote locations; like Command Humanoid, Command Creature, and a few others, which can be hard to find.