Hi Shield-Strength, if you're interested in learning about PvP, we've got a beginner friendly channel/SG/VG on Virtue.
Here's the main thread about it, with a bit of an introduction.
http://boards.cityofheroes.com/showthread.php?t=290219
We hold events for those who are almost strictly PvE looking to learn how to PvP. Then we hold events where you use what you've learned.
While SS/Invul can be strong as in hard to kill, the mechanics in PvP (Travel Suppression slowing you down) along with lag not allowing you to connect hits, and little range to switch targets and contribute damage with the team as effectively, I would not recommend an SS/invul. This is coming from someone who mained an SS/invul brute for over 2 years in PvP. It can be fun sometimes, but with the current state of PvP I could not be as effective as a ranged character.
That being said, I would recommend a ranged character of some type, or a stalker. Being in hide is somewhat like pseudo range, since your opponent can't attack you until you attack them. This allows you a free big melee attack, giving stalkers enough burst to be useful for spikes.
By the end of today, our leaders will have decided upon times for the upcoming events. I'm thinking, 1 event the same as we had (for beginners), 1 that's a little advanced (tricks for those who PvP) and 1 that's actually PvP (Most likely kickball with leaders as the leaders).
Hopefully you can come join us, we're always open to those interested in PvP.