I currently have a Breton Magicka Templar, with most relevant skills leveled (except alliance war and undaunted). She is mostly geared as a healer right now, and she performs well in that role. Her current gear is:

1 Molag Kena (light head)
5 Spell Power Cure (jewelry, shoulders, restoration and destruction staff)
5 Law of Julianos (heavy chest, medium legs, light waist, hands and feet)
Jewelry is arcane, with magicka regeneration glyphs
Restoration staff is powered, with crusher enchantment
Destruction staff is sharpened, with spell damage enchantment
All armor is divines and I use the thief mundus

My buffed stats are:
40.5K magicka | 16K health | 19.5K stamina - they will increase by 6% after I level undaunted and spec the mettle passive
1.4K magicka regeneration (1.55K with repentance slotted) | 65% spell critical | 1.9K spell damage (2.65K buffed with minor + major sorcery and the SPC bonus which is up most of the times from puncturing sweep)
They work well enough for a healer, my heals crit pretty often and I rarely run out of magicka, especially when standing on focus.

But I also want to play as DD sometimes, and I want a 5 piece dropped set, because it includes jewelry, to replace SPC when I DD. I'm aiming for a spell damage above 3K buffed.
Putting spell damage glyphs on jewelry will give 174 x 3 = 522 spell damage. SPC has an 124 spell damage bonus itself, with another 129 coming from 1 piece Kena, so I will need a set that at least compensates those.

One of the sets I have been looking at is Burning Spellwave, which has a 20% chance of giving 600 extra spell damage when you damage an enemy with a fire attack. I'm already running Blockade of Fire as a DoT from back bar. I'm also running reflective light as an opener and self buff (minor sorcery from illuminate class passive). Each of those attacks can potentially proc BSW. However I'm not sure if it procs for every tick or a DoT or just the first damage. This set also adds 124 spell damage (assuming purple jewelry, 2 other pieces gold, same as SPC) and another 688 (3%) spell critical before considering the 5th piece bonus. Ideally I should find a sword for this set, but the probability is very small, so I'm assuming that I will use the jewelry and 2 armor pieces (shoulders, hands or feet) and make Julianos staves. I'm not taking into calculation Maelstrom staves yet since I have not run the arena yet, and the RNG is not favorable for those. One of the main goals of this build is running VMA. Considering just what I have and what I can easily obtain - BSW jewelry - and craft - Julianos - I can boost my unbuffed spell damage to 2.4K, reaching 3K buffed with major and minor sorcery, and further increasing to 3.7K with BSW proc.

If I get a BSW sharpened sword, RNGesus willing, I can also use a 2 piece monster set. I'm considering Grothdarr - still missing the divine light head - or Valkyn Skoria - I have both head and shoulders light divines - since my rotation has at least one DoT up at all times (blockade of fire). Not sure if puncturing sweep is considered as such, and thus will proc Skoria as well. In the case I will be running a sword on the front bar it also opens the question of what I should be running on back bar. Is it necessary to run BSW on the back bar, where my flame spells are, requiring a staff from this set, or will it proc on front bar after I switch, from the DoTs already applied?

I have also considered other 5 piece sets both proc - Overwhelming Surge (proc is weak and single target), Scathing Mage (does not proc DoTs) and Martial Knowledge (procs only one attack and it's only single target) - and non-proc ones, like Silks of the Sun (only boosts flame damage, but the bulk of my damage comes from puncturing), Mother's Sorrow (crit chance is already high enough) and Spinner's Garment (I already have 10K penetration from sharpened weapon and concentration light armor passive).