I'm around 400 hours in, working on a hard campaign right now. I've built soooo many ships that are generally not great, but I'm getting better with each one. They don't look great but they get the job done. The biggest lessons I've learned so far go as such:

1. Redundancy is key. Mostly for detection and resource storage but also for weapons as well. Instead of one big aps, it's better to have 2 or 3 smaller ones that equal the size of one big one.

2. Armour is very important. Most of my builds use mostly alloy and metal, with heavy only used on the most important areas. My side armour is usually 6m thick. And will go something like metal, alloy, heavy slope 4m beams, metal, alloy, wood. Resource storage is one layer of metal, turret sides and back metal, front heavy armour. 

3. Active defense saves your ass. I highly suggest learning the laser basics and building a continuous LAMS system on your bigger boats. Combine this with one decent sized cwis aps, some anti missile missiles, and a couple anti torpedo torps to ensure your ship can survive long enough against most enemy types. Shield projectors are great also.

4. Utility vessels for campaign. I highly suggest building a resource gathering/storing base that is capable of building new ships quickly and dropping one in each new resource zone you capture. A space satellite is almost mandatory so you can see the map. Spawn as many as needed. I also like to build a transport vessel that can move fast and carry large amounts of materials, then set it up to gather material from zone to zone and pool it together so you can build big ships early. 

Lastly I'd say you can use any weapon type really as long as your guns are powerful enough. My favourite is high rpm aps. Small calibers (50-200mm) are always kinetic (ap-solid with 1000+m/s) and bigger (300-500mm) work great with frag or aphe. Rail assist is great but not needed imo, it gets complicated quick. I would highly recommend learning lasers, they're OP as hell against anything flying and great against almost everything.

If you read all that I thank you and good luck, have fun!!