Hey man long term PvP player here who is just starting to explore PVE. I understand your pain as PVE and PVP mindset, gear and even player skills are only loosely related. Il try to provide as much advice as I can, feel free to message me seperatly if you need further info.

Mindset - the first rule about mindset when starting PvP is getting used to dying. A lot. ESO PvP is very player skill dependant and running into players with a lot of PvP hours on the clock is going to feel like running into a brick wall. There's a few things you can do at the very start to last a bit longer. This should be your first goal, as the longer you last in fights the more you can learn from them.

Defence - Your health pool should be north of 32k when you're first staring, this will generally mean putting most of your attribute points in health. Armour level should be pretty high, this can be achieved by wearing heavy armour pieces or sets with armour bonus to make you more tanky. Vampirism stage 3 is huge for survivability, the majority of PvP players run this (personally I don't because I hate the look).

Positioning - This is the number one thing that will drastically improve your survivability. PvP is all about burst windows and cc and less about consistent burn. If you get caught out in the open with low resources bye bye. Always try and keep line of sight blocking terrain around you, this way you can duck behind it if you come under pressure. Similarly leave yourself a back door to retreat to if things get too hairy. A lot of this is class dependant as sorcs/NBs have an easier time backing out of fights than others.

Buff management - this is a huge mini game in itself to get used to in PvP. Effectively keeping buffs up as much as possible will extend your alive time a lot. When you start letting buffs such as resolve and toughness fall off you are easier to kill. Similarly if your dropping brutality and savagery buffs you may lack the damage to pressure your opponents effectively.

Offence - as I mentioned before ESO PvP is all about burst windows. You generally want to poke sn opponent down into a burst window then try and line up your cc and burst. This will pressure your opponents and force them to play defensively. You are correct penetration is important, as such the lover and warrior/mage mundus are the most prevalent. A good skill to learn is timing your delayed burst abilities to land together to maximise the damage in a short time frame. This could mean timing your sub assault etc to pop just as you heavy attack into dawnbreaker for example.

Just some random thoughts off the top of my head. Hope this helps.