If you look at the bitcoin market in October in the past years, it can be understood that it was always positive, but no one can say whether this October will be positive or negative. But OP, if you have a desire and have enough opportunities to invest, you can invest in early October.
Just because the market was showing positive last year October does not mean that it most be positive this year October we know how crazy that the market can be and the least thing is that you can not actually be able to predict exactly what will happen in the market so you don't predict because even with your predictions you can still fail that is one of the confusion that investing in bitcoin comes with you can not always get it right you have to take your time to have actually understanding of how this things works.
And any one that is always judging and relying on what happened in the previous years is not yet serious with investing in bitcoin, any sec you either have it in mind to have an increase or a decrease of bitcoin is trying to breakthrough a particular price, you most be ready to get your self prepared with all this so that you don't have to worry about your price.