Do I need a record cleaning machine

I agree with Xiekitchen.
In my opinion it's a must, and I prefer to use the Audio Intelligent Vinyl Solutions Enzymatic Formula solution.

can anyone suggest a manual system for cleaning lp's?

Steaming is a great way to lift the dirt but then you need to wash it away.

Taters you may be buying new now but if you are just getting into vinyl you will most certainly be purchasing used also. I cleaned my vinyl in many different ways manually. When i realized i would be buying a lot of vinyl because of its superior sound getting a RCM was a no brainer. Ease of use for one and if you include a steamer the results are fantastic. The low cost VPI 16.5 does all thats needed and will pay for its self with the time saved cleaning your collection and new purchases. If you are going to get a few lps here and there then search manual cleaning methods. All vinyl new and used needs to be cleaned to achieve the best sound.

I use an old Keith Monks Record Cleaner. Easy, cheap, effective and does the trick. Bit noisy though. I agree with the others - a wet cleaner is pretty essential if you have any sized record collection.

Charlie