You must have 50% of the total market cap to really be able to pump or dump,
but not necessarily in that way your money will come back, because the world of cryptocurrency is full of risks that are not expected to diga
or even you can use 1000 USD to pay for some of the top media in releasing false news, that is the most effective way
It actually depends on what you are influencing really. In most cases, if you are trying to influence a market with a small market cap, there is every chance you may not need so much to do that, but you also have to consider the possibilities of actually getting to see market participants when it comes to such coins.
I have seen some coins with trading volume most especially of less than 2BTC, so in such cases, these are markets that can easily be manipulated and moved by any whale after accumulating a lot, but like I said, you will still need to be sure of the market you are trying to move, which in most cases, markets in conditions like this, are usually more of shit coins.