It only depends on the amount you are ready to invest, start from "Simple House" to increase population and "Job Center" to generate SIM tokens. There are 2 ways to get your cards that is the Buy option where you can get random cards so it is a form of gambling as u can get some cheap cards or rares. For starters i suggest the Market and first verify the prices as most are sold for either SWAP.HIVE or SIM so search for card and veriffy which is cheaper by comparing the currency prices. Anything beyond that as well as what to increase further i am still trying to get a grasp of ... Especially the Military Industrial Complex that i got yesterday was showing income of ~70 SIM but today is 0 as shown on the above image ... so the first 2 structures i mentioned are the starter cards that are a must have before you go any further like "Ad Agency" that further increases your income and making sure to continue balancing the housing and income cards . Than you get in to "School" or "Reserch Center" for training points to convert Immigrants and Homeless in to Workers. What i did there is an overkill as the structures require higher population than what i have available so taking it slow is the correct way to go.