Why wouldn’t it just be a simple order book? You could easily manipulate it by stacking a bunch of orders just outside the book’s depth, pushing the market in your desired direction. This creates the illusion of ‘smart money’ at play, and with low liquidity, others would quickly follow suit. This strategy would be cheap and surprisingly effective in thinly traded markets.
I am guessing you would be on the hook for the other side of the bet. Apart from the potential legal implications, that could be expensive.
That’s what spread betting is in the uk no?