Things you listed require 3 different builds...
Taleof2Cities wrote: »Are you looking for one all-around good set that can cover all of these?
Or, separate gear sets for each type of content??
Alcast has the basics for all of these on his site. It's a good starting point.
A build basically comprises the following elements:
1. Gear
2. Skills and CP
3. Rotation / Strategy
So do you need help deciding which gear to chase?
There are a pretty large number of viable sets to go with. Julianos is a set that is easy to get (being crafted), and performs basically as well as most other good sets, so it is perfect to start with and may end up staying with you. It's not just a "starter set." It competes with other top tier gear sets. That said, look at sets like Necropotence, Netch's Touch, Scathing Mage, Mother's Sorrow, Spinner's, Lich, Shacklebreaker, Amberplasm, Alteration Mastery, Willpower, etc. You can usually go full damage in PvE, but need to build more for sustain in PvP.
Do you need help deciding which skills to use?
First you need to consider your desired playstyle. Do you want to unleash massive area damage, single target burst, crowd control, mixing damage with healing? The skills you choose for your bar need to reflect your preferred playstyle and show an understanding of the environment they will be used it. For example, ground AOE's like Liquid Lightning and Blockade of Elements are great in PvE because npc mobs are stupid and stand in them. Players will try to avoid them, so they will be much less useful in PvP. CP choices should flow out of what skills are your highest priority. Choose things that boost those.
Do you need help developing a rotation or strategy?
Take a look at the gear and skills you want to work with. How can you maximize your damage output in the use of these skill? Perhaps it's a static PvE rotation if buffing, dropping dots, heavy attacking, and/or using some spamable skill. Maybe it's more about getting a burst combo down for PvP and knowing how to react to things that your opponents do.
My point in laying all of this out is that with a question such as that in the OP, the lack of specificity leads to an implied request: "Teach me how to play a mag Sorc in ESO." Not that this is a bad question, but it is something that's difficult to accomplish in a forum post, and is much broader than just suggesting one or two gear sets.