I picked up EotE as something new to play, right now i'm running the adventure modules to help everyone get familiar with the system as a whole.

What i'm wondering is if anybody can give some tips on building a complete custom game?

To build a custom game, first think up the first encounter to get the pcs involved with the story (Think up the story also). Next make the bad guys for the campaign and put new encounters in. When you get near the ending, create the nemesis and make the pcs fight him/her (not the final battle). Then create the final encounter and get everything ready for the finale.

Boom!

And that is my tips for you.

My suggestion - keep running the canned games until you get your feet under you. There's tons and tons of them out there, so plenty of stuff to get used running the game. Then you can branch out.

Also, this might be of help: The GM Handbook

Start with the adventures from the starter boxes. I started with the EotE adventure (Escape from Mos Shuuta) and continued with the Bonus adventure (Long arm of the Hutt). After these, my players are free to go wherever they want. I have prepared some information, that will lead them to other pre-written adventures, some lead to smaller encounters (bounty jobs) and some may end up getting in contact with the rebellion.

I like to keep my ideas and plot hooks generic enough to settle them on nearly any planet the PCs will travel.

Here are my handouts I gave to the players. They are in german, but maybe you get an idea:

https://www.dropbox.com/sh/z66g193p6o1gi5j/AACTglcvZQi3JXv-o7UbTHZta?dl=0

If you're planning an ongoing campaign, incorporate a strongly bonding moment/encounter for the PCs early. It is going to be helpful, when questions arise like "why should I help them with their personal problems?", "what's in it for me?" etc. Best buddies make for a much better group than business associates.

I found this post to be full of useful tips: