Artificats are just really expensive items that you can buy from the artifact shop.

What your thinking of are Favour Items. After each game you are awarded with Favour Points, which can be used to purchase a Favour Item at the start of each game. Favour Points are persistent (carry over to the next game) and as are Favour Items (if you purchase one you will stay have it bought next game).

after a solid day of play.. ive only managed to unlock 4-5 of them - altho that includes 2 of the more expensive ones..

would probably take a week of playing too much.. maybe a month+ of casual play

I just bought the plus 15% movement speed boots. They seem to work well enough.

My favorites are the +10% exp

and there is one that gives +400 health, +5 health per second and reduces death penalty by 10%.  Another book does +400 health, +5 health per second, and gives minons +x damage or armor or something (for oak only).  Some items are demigod specific.

You pick one favor item when you start the game and then you can't change it during the game. You can wait until you know what you're facing before picking one, but once you do you won't be able to take another.

Favor items are in the item slot farthest right on your little HUD at the bottom of the screen.  Different game modes have separate favor totals (IE single vs multiplayer).  Once you buy a favor item in single or multi, you will never have to pay favor in that mode again (unless favor totals/favor items are reset).  So if you just want the +15% movement speed item, you pay favor points for it the first time, and it will unlock it.  If you pick it again in a future game, it won't cost you any favor points.  So in essence, you're paying favor points to unlock a particular favor item the first time, and any picks of it in the future are free.  As people said though, once you pick a favor item in a particular game, you're locked into that item for the rest of the game.