Do the in-game tutorial for the first steps. You'll gain some level easily.
After that a common mistake is to discover a lot of different ship types. Stick to one and get it to a higher level. Space Hunter is a great ship.
This will lead you easily to mission 40. Well, you need to upgrade your capital and space station to increase your fleet count, too. Those two buildings are also the most important ones.
Always do the daily task up to the 50 free Space Bux. You can buy Diamond VIP with them for 24/7, this is a very good investment.
Later on you'll need a long range ship type, like Hamdar or Charybdis.
Try to do all the elite missions you can do. They will give you custom blue prints and shards to level up your captains. Both very important.
== What's next? ==
You need resources. Lay Siege is the way to get more resources. Your high level Space Hunter will help a lot. But it will do only impact damage. So you need some other damage types, too. Get Spinner, which is also a great ship and it's doing heat damage. Later on you can pick Charybdis for explosive damage - up to level 4. Don't spent too much of your medals and honor into the predefined ship models. Use them for your customs instead.
Use your shards to promote a captain with a high Evasion value. You need a high stack size especially for your tank captain. This is the one who will go to Minimum Range and attracts the fire. Your other fleets can stay behind with Maximum Range and shoots the enemy down with hopefully no losses. Ship based weapons with a range of 6-10 will work very well.
Join a good guild and ask the more experienced player for further tips. Have fun.