You get star coins from Pandas and Coin quests, and if you invest in your island to create higher level items you can sell, then you can buy enough LSs to get a steady stream of SC from quests alone. Once you 'fight' your way to L70 you get The Pathfinder ship and the quests there yield 5k !! SC per week.
This game is a game of time, patience and investment into your island - without the island development, there is no progression.
As for premium, you have to use gems - buy a gem pit (save up all your levelling up and weekly gems, or buy) and place it. Once you have enough gems for next pit, buy it, then the next and the next. DO NOT use gems for anything that can be bought in trade. You will amass enough gems for permanent prem for years.
If everything was so easy and handed out on a plate, the game would be no challenge. We ALL started at L1 with just a Mayor's house and invested time and resources to get where we are. The more time and resources you invest, the easier it becomes.
The game IS the game. We ALL have the exact same challenges - adapt and find ways to 'beat' the game.
ummm many players have already used up the maximum number of gems pits allowed by the game.