We know they do heal instantly instead of taking time to fill up as regular potions do though the mana and healing potions seem a little useless due to their rather small heal amounts. You can just save all your grinderella and plumbago until you are ready to do tier 3 combines even if this sounds useful to you. Making the potions and storing them takes a LOT more space, and you are really going to like what they become in tier 3.

Tier two requires you to be level(metin2 yang) 30 and go to the second town of your respective kingdom and find Thomas. You will remember him as the spy you had to speak to for several lower level quests. Choose the alchemy option when you click on him and prepare to make some slightly more useful potions.

Jamul + Elixer of Agility which is Basic Resist (Not EXACTLY sure what this boosts, it doesnt change any visible stats on the character screen).
Jamul + Elixer of Strength you will be Double Attack (Gives a significant chance to critical attack for 3 minutes).
Ganoderma + Healing Potion x100 = Greater Healing Potion x100 (Instantly restores 100hp).
Ganoderma + Mana Potion x100 = Greater Mana Potion x100 (Instantly restores 100mp).

You can just save the herbs for tier 3 stuff even though the HP or Mana potions are now a bit larger they are still quite small, its just not worth wasting the possible tier 3 potions to use these quite small heals. Just have fun in Metin2.