I hear a lot of people asking about the best way or best approach to building a fun and solid deck. It all starts with what you want to focus on. Do you want lots of units, or plenty of resources, maybe a game mechanic like capturing or consistantly winning the force struggle or punishing enemies for committing to the force.
Once you have figured what you want the goal of your deck to be, go through all the objectives for each faction for that side of the force. Mixing factions is okay but make sure that one is more dominant than the other. And use the faction card for the least dominant faction so that you are ensured to always have a resource to pay for any of those cards you draw to meet the resource match.
Once you have picked out the best objectives to achieve your goal (there may be a lot more than 10 or even 20 objectives) begin fine tuning your selections by taking out objectives that don't offer any serious advantages or help you than just meeting your goal. Good things to look for are units with good spread of icons both combat and force. Other pros would be edge cards and resource cards. And always be mindful of the factions. Try to keep your deck to two factions. Playing a three faction deck would very difficult at this point in the evolution of the game. But in the future this may be possible.
Once you have narrowed down you list of objectives to two factions or even one faction, try to get your list of objectives down to ten. After you have at least a ten card objective deck find someone to play-test your deck with and see how it performs. Play a few games with it to get the feel for it. You rarely get used to how a deck plays after a game or two. You need a few to truly stretch it's legs and find it's flaws.
And from there tweek it to your desired specifications by either adding or replacing objective sets or trading factions.
Hopefully this was helpful to all who read and needed a little assistance with deck creation. Happy gaming everyone and remember to just have fun and enjoy the game be a good sport.