I just teleported close to my alliance, but now I can’t find any marauders that my combat hero�..

The maruaders spawn randomly in the world but the closer to the center of the map you are the higher the level is likely to be. You may still be able to find low level one near you or if not look closer to the outside edge of the map. If you have the recent update then you should find a search option (magnifying glass on the lower left) to let you search for specific level targets.

To get stronger you need more troops, higher level troops, stronger heroes and more heroes. - Upgrade the training grounds, Compete the legion research, complete troop related research. Upgrade the stable, barracks and archery to get to higher level troops. Recruit orange heroes and use wisdom medals to unlock and upgrade skills. These are all tasks that you will be doing to progress in the game and your power will go up as you progress at whatever speed you want.