1. Regarding resources. Use the resource screen that shows the number of sources you have for each strategic and luxury resource. It will show the units in stock, the galactic demand, units in transit, and units unfilled. You literally have to learn how to read this one and act on it to get good at this game.
You will get a lot of recommendations on how many sources of each you need and have to find your own balance - and part of it depends on whether you start prewar or not. But I prefer to get the following as soon as I can - 10-15 steel, 10-15 calson, 4-5 each of lead, gold and iridium, and then at least one each of every other strategic resource. After that, I want to get at least three of each strategic resources as soon as possible.
2. Regarding big mining stations versus small mining stations. Again, my preference is to put four 4 mining extractors and 2 luxury exactors on each mining station; on a gas station, I put 4 gas extractors and 2 luxury exactors on each gas mining station. Part of this is just lazy on my part. It means I only need two mining stations - on gas and one mineral. Other people custom design a lot of different mining stations. I just find it too much trouble but that me. I also usually put 30 standard cargo bays on each mining station.
3. Regarding cargo bays on spaceports. Depending on who you ask, you actually need zero. I have never had the guts to do that and put 6 on a small station, 8 on medium, and 10 on a large. This fits with my personal belief that a spaceport needs cargo bays. But some pretty smart people have run some simulations here and determined that you actually don't have to have any.
Last, but not least, welcome to the forum. The people here are good folks who are more than happy to answer questions (I have posted a number and had a great response), so if you have any, I would encourage you to post. Most of the time, you will get a number of responses very quickly.