Lol, you make me laugh, you sound as though we are discussing about one of those shitcoins/scam projects.  Well for bitcoin there is no need for that because your little buying club would only end up as a little pebble thrown in an ocean. Even if you manage to manipulate the market, the market price always recovers from manipulations and keeps on to its movement. Bitcoin is not a shit project or just some random currency pair that can be manipulated anyhow. I could remember sometimes last year before the halving when Grayscale sold a large amount of bitcoin, the effect of that was a huge dip but today if you compare the difference is price from the dip, you'll observe that bitcoin cannot be manipulated for a long period of time. Bitcoin price is where it is today because of trust and results it has yielded for the passed few years from the genesis block. However I advise you buy what you can, because no matter the strategy you employ, if you hold for long term you'll definitely get profiting results.