If you are completely new to the game and want some basic mission suggestions, I would give the following suggestions.
Mission Tips for Newbies
After you land on New Atlantis, most of the missions there are fairly short and give credits and XP. For some decent starting rewards, go to Cydonia on Mars in Sol system which is near Alpha Centauri system. I would recommend sticking with New Atlantis for the credits and XP first though.
Once you get to Cydonia on Mars, comb the whole place and you will find many quest givers with varying kinds of quests. Some of the differences here will be suit pieces and weapons. I’m not saying every mission will do this, but there are more quest rewards hanging out here than New Atlantis. Also, the vendor on the left after coming in (Denis Averin at the UC Exchange), way down on the end before you go down the stairs to the mining area, has a repeatable line of quests where POI’s are generated. This can be nice for at least one trip to get some base-clearing gameplay in with both loot (I think a lot of loot for the level), credits, XP and rewards.
I also like the unique feel of Mars, which may not be to everyone’s liking but it’s so different from New Atlantis. The low gravity is also nice for the early game weight issues which is a huge plus for dealing with that. The hub won’t knock your socks off, but it’s a nice place to hang and level up, loot up and soak in the experience. Has a nice feel to it.
Also, for the loading screen haters I’d say Cydonia is an exception to the loading screen issues in the bigger cities. There’s a couple places that had to be partitioned but once you enter you don’t (for the most part) transition until you leave the colony again. I think only the living quarters area has it’s own instance. I could be wrong, and I may not have found everything there is to find.