This is a startergy that I have used on solo myself.

Rounds 1-2 stay in the main room by the lander
Round 1 Knife only
Round 2 5 shots from the pistols one knife
Rounds 3-4 Building what jugger-nog is in.
Round 3 At beginning of the round open the bottom door and buy the door at on the floor where you start off and buy the MPL. Shoot the zombies with 3 bullets each then knife.
Roound 4 By this time you should of got enough points to open the next door and buy the skateout(Get rid of pistol). You go outside the building then camp here with the skateout for one round.
Rounds 5-8
Round 5 you can either go turn on the power and use the mystery box or camp by the phd flopper lander and buy the mp5k to get rid of the MPL.
Round 6 Just do the same as round 5 but if you haven't camped at the phd flopper lander do that now and buy the mp5k to get rid of the MPL. At the end of the round get a crawler and go turn on the power and try the mystery box until your credits go to 1000 out or you get teddy bear or get a ray gun or thunder gun or both.
Round 7 camp by phd flopper and at the end of the round buy jugger-nog.
Round 8 Camp by phd flopper agin but have the lander there just in case. leave one zombie alive at the end of the round then go buy all the places where the landers are and use them now go back to the power room and lauch the rocket if you have a ray gun shoot it down(you get a power up). Make sure you have 1250 credits left at the end of the round so that you can get the PaP machine.
Rounds 9-100 Camp at the phd flopper lander and have it there just in case it is recommended to buy all the doors so that you can run around the map at your will.
Rounds 100+ your on your own