When you first start out, potions are the key. However, because you can only identify the first attribute of any ingredients, there's not many potions that are useful. Carrying capacity (weight concerns) are also very important early on. So this list concentrates solely on potions that are very lightweight with easy to obtain ingredients. I'm assuming that you have a full set of Novice level Alchemy equipment. Any listed effects were calculated at Alchemy level 20 (with Luck of 65).

Note: Obscuro's Oblivion Overhaul (OOO) or one of the other mods that I have installed plays with ingredient weights. So the un-modified version of Oblivion will result in higher potion weights. Note that the first potion of a particular name and strength sets the weight for all other potions created under that particular name and strength. So use the lightest weight ingredients first (make a single potion) then use heavier ingredients until you see the potion effects change (when your Alchemy skill increases).

Poison (Health) (0.1 weight)
- Combine (2) of Nightshade (0.1), Stinkhorn Cap (0.1), or Wisp Stalk Caps (0.1)
- Damage Health: 3 pts for 10 sec (30 total)

Restore Health (0.05 best weight)
- Combine Cairn Bolete Cap (0.1) with Lady's Mantle Leaves (0.0)
- You can also use Venison (2.0)
- Restore Health: 3 pts for 11 sec (33 total)

Restore Magicka (0.05 best weight)
- Combine Flax Seeds (0.0) with either Bog Beacon Asco Cap (0.1) or Steel-Blue Entoloma Cap (0.1)
- Restore Magicka: 5 pts for 18 sec (90 total)

At early levels, those are the major (3) potions/poisons that you should be carrying. I'd also suggest carrying a few of the stronger store-bought (or looted) Restore Health potions (which can restore 60-120 points very quickly). Other potions are either too heavy, too limited in duration, or are better off used as merchant fodder.