My mageplar is primarily pve dps altmer. I have pvpd a lot on him on and off for years.

His current gear is bright throats, bloodspawn/grothdar x 2 heavy and crafty alfiq. Lightning staff front bar and sword and shield backbar.

Basically ill use extended ritual, rune focus and dampen magicka for buffs, hit degeneration, vamp bane, purifying light, toppling charge, crescent sweep and jabs all day.

You got your cleanse from ritual and heals from honor the dead and jabs. Solid survivability and damage with heaps of magicka.

I wouldn't go heavy on a damage dealing templar. You lose too much crit and templar has a crit damage passive. You would feel the loss of damage, hence go light. The longer you PvP, the more glass cannon you become and this is totally viable on magplar, because you can compensate with heals, notably Sweeps, Living Dark, Extended Ritual and, of course, Honor the Dead.

For starting out I would recommend light armor, 2x damage sets or 1x damage, 1x sustain set. Lots of things are viable and near-equivalent. Front bar sets: Overwhelming Surge, New Moon Acolyte, Auroran's Thunder, Spinner, maybe Spell Strategist. Body sets: Bright Throat's, Amber Plasm, Shacklebreaker. I'd actually recommend Amber Plasm, unless you want to use Restoring Focus for stamina sustain (break free / dodge rolls).

Back bar set: Blessing of Potentates (1H+S or resto) or vMA resto. You could also back bar Lich. This would allow you to wear 2x Potentates jewelry, which is then active on both bars.

1H+S is tankier, but resto plays better for attack as you cast, for example, Light Attack -> Degeneration from a distance, then bar swap and move in with, say, Toppling Charge, having activated your back bar enchant. Back barring Spell Strategist is another option you could use.

Monster sets: I'd recommend two resistance pieces for starters, such as 1x Pirate, 1x Chudan. Bloodspawn would give you some extra stam sustain, but for tankiness it's hit and miss, while Crescent Sweep is so cheap you hardly need the ulti gen. Troll King: I'd prefer the two resistance pieces on templar. Skoria is an option as is Grothdarr or even Zaan. To make Zaan work, though, you might want some Swift jewelry or at least be prepared to spam Toppling Charge.

Cyrodiil's Light is a nifty set, but getting the most out of it is build-specific. While it helps you stay on attack, it's not really a defensive set unless you run the Phalanx build, an old build that uses Meditate for sustain and Mist Form for defense. While Cyro's Light is active on Sweeps and Radiant, the key idea behind that build was that it's also active during Meditate and Mist and that people would interrupt your Meditate, which would allow you to cast something expensive (Mist) for free afterwards.