Lawn Tractor Won't Start?

I have an old Dynamark lawn mower that I decided to fix up this summer and I am stuck. It didn't start and only clicked once when I turned the key, so it didn't turn over. I replaced the battery, put in gas and oil (drained both before adding new) and it started right up. After idling for a while, I put it into gear and drove for about 10 feet and it died. It didn't really slowly die it was a quick cut off. A small amount of smoke came out near the air filter and in the oil container. I haven't got it to start since then. I took off the engine cover and found dirt/leaves on the engine and figured that's where the air filter smoke came from. I don't know why there was smoke in the oil container when I took out the dipstick. I replaced the spark plug and still no luck. What should I do? Also, I found a very small amount of oil in the bottom of the air filter holder after it died.