The Dlc that you still can play is orsinium ( wrothgar) , imperial city, thieves guild dlc and in a few weeks the dark brotherhood dlc.

For min-maxing race can be a really important component but if you aren't in to min -maxing that much you can do every content what there is without having the best gear/race/class etc.. Also for trials they are starting to introduce normal modes to make it easier for people who doesn't want to min-max while still give them the content and group play out there. such as normal, Maelstrom arena, Maw of lorkhaj normal and soon Sanctum ophidia will have a normal/veteran version as well.

Also for pvp/craglorn you can group up with a few members maybe friends who never done it before and are interested in doing them.

As for gear you should look on the internet/famous youtubers they have plenty pvp/pve builds that are quite good and which you can use to suit your game style the best.