I am not able to conquer territory for doomsday conquest, the game tells me spots are to strong. What..

You need to start with low level plots. Initially you can only capture the plots in the outer edges of the map and you need to start near your alliance center 1 or other alliance members plots. Check your map for your alliance center, nearest the edge of the state.

Start with any empty plots and level 1 plots and then move on.