A lot of people have the same questions about Kingdom Conquest, so rather than typing them out on my iPhone, I’ll just put some info up here.
First and most importantly, always work towards a quest goal, as they will give you a very nice boost in resources as you complete them. The highest quests I got up to on world 7 were the 1000 resource ones, which gave (I believe) 3500 of each resource. I also got up to conquering a level 4 territory (which was very tough), so they seem to go on for quite a while.
Related to the above, try to focus on increasing your resource gains before really working on monsters and units. The building needed to increase unit size beyond 4.0 (the starting size) is very expensive, and you will also need another building before that to open up the middle (rear) slot. Before you go after that, try to get AT LEAST 1000+ of each resource coming in, preferably 1500+.
One final note about resources: level up your warehouse until it can hold 7900 resources (level 5 I believe), or higher if you don’t play daily. This will prevent resources from being ‘wasted’ when you cap out. This is especially important when completing quests, because if a reward puts you over your current limit, the excess will be wasted.
For monsters, you want to keep the count as low as possible at all times to free up food income. This means that when you gain a new monster from a pack, you should use it to attack a level 2 territory. It likely won’t win, but it will drop its count to 1, and also earn it some XP. The other option you have is to synthesize the monster, which can be useful to skill up your ‘main’ monsters primary skill or to give it new ones (there are quests explaining this)
As the goal of the game is to capture towers, look around your starting area and start grabbing land in the direction of the tower. Wait to build your base (also explained in a quest) until you are one square away from a tower, as this will cut down on travel time/fatigue when attacking. If you have an aggressive neighbor, position your base accordingly.
The ‘best’ starter unit I’ve found is a goblin archery as the leader, and a goblin warrior at the front. The warrior is a 2.5 count monster, while the archery has range 3 and is 1.5 count, giving you a maxed out 4.0 unit. Both can usually be found on the auction house for cheap, and are also fairly common in packs. The 2.5 lizard unit is also very strong, and likewise can be paired with an archer. Try to use this unit as often as possible, as you will have quests asking you to conquer higher and higher level territories.
Items from packs: You can’t sell or trade the weapons/shields/rings you get, so as soon as you no longer need something, it’s best to trash it (warehouse, little trash icon on the card itself) to reduce clutter.
When doing the dungeons, it’s always best to wait for 4 people, as this will ensure you finish and get the two pack bonus, plus cut down the amount of time it takes to clear one out. 3 is usually fine if things are slow.