Happiness is striking a balance between current population and maximum population. In the early game, Colony ships will take some of your population which will increase happiness. This will also lower raw production a little bit. This can be offset by building factories.
Later in the game, you can build improvements that will increase happiness. Although there are benefits to having 100% happiness, it is a difficult goal to maintain. I generally aim for 60% or better on each planet. Some will disagree with me on this. I just think there are more important things to worry about.
Cities and farms can come a little later. Find a planet that is well-suited to farming and devote it to farming only. Farms generate food for your entire civilization, not just the planet they are built on. Don't waste valuable tiles on your planets for farming.
I only build cities on high quality planets where population matters. These would include large planets devoted to Research or Production.
Money is rarely an issue in GC3 and in most situations I tend to ignore it. With a couple Survey ships and the occasional Treasure Hunt, you'll get all the cash you will need, and it gets easier as time goes by.
I am by no means an expert GC3 player, but I think the above tips should at least get you started in the right direction.
Hope this helps,