To expand outwards with land select the Expand option from the marketplace.
The number of tiles you're allowed to own at any one time is connected to your current level.
To upgrade all of the robots you own, you're going to need to feed them with produce created by the Snax Shacks.
The higher level robots are, the more money they'll generate.
Keep an eye on the Goals section of the interface. This will give you new objectives to work towards and will reward you with some great cash bonuses if you take part.
To visit a friend's planet, click on the Friends interface button at the bottom of the screen.
You can both sell and move awkwardly placed facilities and even though you won't get the full amount back it's better than nothing.
From the market section you can view the role of each robot by clicking on them individually, but they also have an icon which tells you at a glance where they should be deployed. Use this to plan your building moves.