As an alternative to Blood Magic?
I have tried that. My character building is poor but I can't seem to run auras and use skills even if using Mana Leech which is why I was interested in trying bmI though if I built a heavy life character with life gain on hit, I could then use finally 2 auras if I used blood magic.
Maybe I am just completely screwing this thought process up.
It's very hard to answer the question in general terms, since there are maybe half a dozen ways to do it and your mana consumption and regen will be changing as you level. It's going to depend on a number of factors with your build, and there are a few ways to tweak things:1. Change your support gems around. Sometimes while you're levelling, support gems have too high a mana cost multiplier (e.g. Chain has a 200% mana multiplier, so it's often hard to use that support gem, but you can possibly swap in Fork, which has a 125% multiplier). Some support gems have no mana multiplier at all (Blind, Mana Leech, Additional Accuracy, etc) and Reduced Mana has a negative mana multiplier, which is obviously helpful.
2. Get Mana Regen from the tree or your gear. It depends on your particular tree, but if there are convenient regen nodes, they can help a ton while you're levelling and you can always respec out of them later. This is just a for-instance but if you can swap an Atziri's Foible into your amulet spot, it's very unlikely you'll have mana issues with your build.
3. Increase your mana pool with +mana on gear. The higher your overall mana pool, the higher your base mana regen rate.
4. Run the Clarity aura. Clarity is a balancing act - the reserved mana goes up with every level, as does the regen. Sometimes a level 5 Clarity is ok, sometimes you want to take it all the way up to 20. Also, you can tweak this with Aura nodes on the tree - some reduce the mana reserved by your auras, others increase the effects of your auras without increasing their cost (in this case giving your Clarity more mana regen).
5. Mana pots - self-explanatory. I almost never use mana pots, although sometimes I keep an emergency one (seething or bubbling).
The Mana Leech gem is an option, but it's currently pretty terrible and very few endgame builds use it. It may work for you while levelling (I never use it) but endgame you're almost always better off using the gem slot on something else.
If instead you decide to go with blood magic on your skills, it's now a question of balancing life leech, life regen, and life on hit with your skill cost, and again this will be build-dependent, but with a very big cost - the Blood Magic gem has a 245% mana multiplier (goes down to just below 200% at level 20), so your skills will cost a lot more life than they cost mana. As a general rule of thumb, life on hit results in more leech at lower levels (when your dps is lower) and life leech surpasses life on hit in terms of effectiveness after your dps reaches a certain level. With a level 20 Life on Hit gem and a level 20 Life Leech gem, the Leech gem surpasses the Hit gem when your damage per hit is higher than 500, although in practice that number is probably more like 750 since Life on Hit is instantaneous and Leech is leeched back over time.