I am level 79 and for a good part of that journey I was focused on investing in perks that have a direct payoff in dealing damage or reducing damage taken. Over time I got real tired of constantly having to go from merchant to merchant to sell all my loot off and acquire materiels for smithing, enchanting, and alchemy. On a whim I decided to start taking some of the merchant based speech perks. I eventually went all the way up the left side of the speech tree. I have to say that this has made the game much more enjoyable as I can now sell everything off and buy what I need very quickly. I used to have very little money and lots of expensive crafted items that the vendors couldn't even afford to buy. Once I took the perks it was not time before I was walking around with 100,000+ gold. I can now trade any item with any merchant and all of the merchants have much more money available for trading. It might be a glitch but the riverwood trader has over 10,000 god available for trading whenever I go. Anyway if you do alot of the crafting skills and need to buy/sell alot of stuff you should seriously consiser the merchant skill perks from the speech tree.
I always invest points into the Speech Tree.
The only ones, I do not take is, Persuasion, Intimidate, Fence and Master Trader. Lots of folks say the tree is useless, I however beg to differ, being able to sell any item to any merchant is alone worth it.