Make good use of your siphoning skills, as they will keep you alive. You should be able to completely keep yourself alive with those. Swallow soul/funnel health should be one of your main skills to use. Sap essence is a great AOE skill that also heals you. Make sure to run Siphoning Attacks while in battle to keep your magicka up.

For magicka, you want to likely be using a destruction staff on your front bar and either destruction or restoration staff on your back bar. If you are having trouble surviving with the siphoning skills, use the restoration staff on your back bar to help survive better.

Make sure your gear is properly leveled up to your level. You want to keep it relatively close to your level. You will start seeing problems if it's 8 or more levels behind you. As a magicka character, you should be looking to use gear that gives you magicka, spell damage, spell crit and magicka recovery.

Make sure to use food. Preferably, you will want to have food that adds health and magicka. At the very least, food for health. You want your health to be at least 15k with food, but probably more since you are less experienced. Magicka should have the rest.