If you really just want to beat a computer 1v1, here's what you do.
To start off, send one worker to build a Blacksmith and another to build a Barracks, and the last worker to mine gold. Set your Swordsmen and Archer into a position where you know the enemy will attack you. Make 4 more workers at the castle. Make the first one that comes out mine gold until you have 100, and another one mine stone (until you have 500, this is just in case you need to build more Castles/your Barracks/Blacksmith gets destroyed), another one mine wood, and the last one mine gold. When you get 100 with the first one that comes out, build a Farm. Keep all animals in the farm (take the animals and right click on the farm so they go into the middle, if they can). It's your choice whether you want pigs or cows. Cows = save 5 gold compared to 2 pigs. Pigs = if one dies, you have another one for insurance still. Okay, after your Barracks is done, send that worker to mine gold, and when you can, make 3-5 more workers mining gold. When your Blacksmith is done, send that dude to mine wood, and make 1 more worker to mine wood. If you are fast like I am (no conceitedness, I can't even beat one computer ultra and most veterans can beat 3, but I started like 2 months ago), then this will be before the first attack, vs. Magic or Tech. If you are fighting Tech, then you should have about 5 Guards, the 2 Swordsmen, and the Archer when they attack. If you are fighting Magic, you should have 2 Guards, and another one that finishes before the attack is over, but that's all you need to own the Daemons' asses. When you can, making sure that you're ALWAYS making at least 1 Guard, upgrade units' Shield and Melee Attacks, and later Shield (2). This will increase EVERY GUARDS' defensive and offensive power, so it's well worth it. When you have at least 10 Guards, stage you first attack against the enemy. It has a chance of failing, but you can probably do enough damage to ensure that they don't have any flying units when you next attack. Keep making Guards, and when you have about 15, attack again, and you should win. They should not have any flying units if you do it like I do, but if you think you took too long, make some Archers. This is one way to easily defeat any non-ultra enemy on 1v1.