Well everytime i buy 2-3 players seems like for the rest of the season my team can't pick up wins get dominated in no matter what i do to change it i can't help stop any team over running me how do i fix this? also is there anywhere to tell how long it will take them to gel ?
I'd say the main thing is to buy players who have similar personalities to your current squad. You can see this in scout reports under the personality section where it says whether they'll fit in or not. I'd also build my squad around Determined, Professional players because these are likely to have good hidden attributes and will get on with their teammates better.
Another thing that helps is new players already knowing the language of the new team. This helps them gel quicker and produce good performances sooner.