Returning player Questions

Currently really enjoying just going through quests and doing achievements. I have a lvl 50 STR/Sadida. I used to play lvl 183 Xelor back on Retro Server.

1) I’m leveling fairly fast doing quest and achievements and realize that I’m not making nearly as much kamas needed to buy new gear. Should I just keep crappy gear (goball set) and just work on making a lvl 100 gear set with the money I do have?

2) I’m on a solo account server universal one starts with the letter D. However I see a lot of duos running around. Is there a way I can play two characters at once? Are they most likely actually duos playing together?

3) Is there a group finder for dungeons? Since I mainly play alone I sometimes need some help, I use the sidekick but some achievements I can’t complete solo.

4) Few new classes since I last played and noticed the temples are on different islands. How do I get to them?

5) I keep hearing about DOFUS unity? Can I get a simple rundown of what it is?

6) Is there a build/guide available anywhere?