Extra Effect + all 5 ranks of Enchanting +20% (If you only get those perks, each perk spent = about 2-4 perks put into other trees, and you can switch things up).
Math here:
Enchanting Perks (specifically the +100% to enchants and Extra Effect) are the most powerful and flexible in the game.
Many of the magic items seem to have effects that match the tiered perks in other skill trees. So you get a 400% increase to enchants which can round out other skills.
Consider:
Let's say you want to max out your sneak after already getting some other perks in that tree. That'd be an investment of 4 perks at 20% per perk.
Let's see how much +Sneak you'd get with enchanting per perk point.
Assuming a +15% Sneak enchant (which I bet is probably only what you'd get from a Common Soul Gem, but let's just go with that for the sake of example), what could we get?
Well, w/o the Enchanting perks, and applying the enchant to every armor slot (feet, hands, armor, helm, 2x rings, and amulet), we'd have 7*15% = 105% increase.
With the above perks, we'd have a 420% increase to Sneak.
420-105 = 315%
Total perks to get both those perks: 8 perks
315/8 = 39.3% increase to Sneak per Enchanting perk. Roughly double what you'd get investing in the Sneak skill tree directly.
(Also, I ignored that along the path you'd grab +25% to skill increase enchants)
And I seriously doubt that +15% will be the cap for +skill enchants, so the difference is much larger. In fact, I expect it to be more like a 4-5x increase per perk over investing in a particular skill. And the gear you enchant is swapable, unlike the perks. Want to pick a lock? Put on your lock-picking rings& amulet which offer a combined 225% increase to Lockpicking (base 15% but including the 25% perk in tree). Switch back to your +whatever other skill when done.
Any build that doesn't go with the aforementioned Enchanting perks is either doing it for RP reasons or just hasn't thought through the game mechanics enough.