Just returned and have some questions...Follow

Hi all! Just recently decided to come back to the game after not playing regularly since like 2009. Played a little bit during Abyssea but not to much. I read the returning guide but still have a few questions:

I'm using my old account and I did a little leveling in Abyssea so I have a WHM at 80, RDM at 80 and BLM is still at 75. I think I have done the limit break to access 85 but not for certain on that. Can I solo all these limit breaks and then level my jobs up without an Abyssea party? Thinking on getting BLM to 99 first. So can I do fields of Valor to level it up to 99? Where would I start leveling at 75 for BLM? I think these limit breaks need Kindred Crests, are these found in Abyssea?

My gear is all obsolete I'm sure, do I need to worry about acquiring new gear or not yet? Should I just worry about getting to 99 and then find gear or do I need some new gear right now? My BLM has gear that was good when 75 was still level cap. Same with WHM and RDM has no gear.

I haven't purchased the Seekers expansion yet, do I need to get this yet or can I wait till I'm 99? I'm not sure where I'm heading, I guess just level up to 99 then can I head over to the new zones that come with Seekers and do some end game content or at least some missions to grab new gear?

Also, do people do the end game stuff with other players still or do they just solo it with Trusts I read about? I'm hoping if I get to some of the new missions/end game content to work with some other players. I understand leveling is kind of a solo thing now but are the rest of the aspects of the game still played in groups?

Finally, I'm on Carbuncle. Haven't found a Linkshell yet, but just ran around in Juneo a little tonight. Is Carbuncle a high enough population to stay there or would I need to move to another server like Asura? I've noticed a lot of people say they are on that server and it's good for newbie players/returning players. Will I need to wait until I get to the new zones to maybe find a social linkshell?

Thanks in advance for any advice, looking forward to playing again but it's a little overwhelming. Hopefully it all works out in time!