Glowing Mushroom, Sabre Cat Tooth, Spriggan Sap, and Blister Wort will create it the 50% bonus to improving weapons and armor from what I read.

However, you can only create a potion with a max of 3 ingrediants right? So how does that work?

I assume any combination of those ingredients would make it...

Two different ingredients are enough to make a potion. But be aware that the strength of the effect depends on your alchemy skill

Thee player cannot create a 50% potion, highest a player can go is life 32%

What? Don't listen to this guy.

You can create a +130% smithing potion with enchanted gear, +169% IIRC with double head pieces and vampire necromage.

You only need two of those ingredients to make that smithing potion, its strength will depend on your level, perks and enchanted gear.