Place your Town Hall in the center and protect it with as many walls as possible. Also put Sheep Cannon near the center to cover as much area as possible. Defensive towers and storage can also be placed inside your walls, while factories, taverns and all other buildings can be placed outside. As soon as you have the resources, repair your Guild House and join a clan by level 20. You will get several new options.
Gems
Complete missions, connect with Facebook, and watch for special offers to earn gems. Spend gems to to speed up building construction.
Heroes
Unlock more heroes as soon as you have the resources. Keep them upgraded through training and battles.
Resources
Gold will be needed more than other resources. Upgrade your Gold Factories first. It is needed to upgrade most of the buildings and the best walls. Nectar will also be important once it becomes available to craft for your heroes to improve them. It is easier to gather more resources in multiplayer battles. Do not worry about the single player missions until you have built up and upgraded your troops.
Units
For early battles, use Archers for long range attacks after sending out your Warriors. Keep upgrading your Taverns as much as possible as you will eventually need to switch to more advanced troops. Sending out troops that get the most resources at the lowest cost. Watch the upgrade tree to what becomes available. Focus on getting the most important ones.