Hi Guys, I am currently creating a rts game. I have already created my camera and some characters which i can move when clicking. But now I really have no idea what to implement more in this game… Could you guys help me?
There is a lot going on in an RTS game, so you have a lot to pick from. But from my point of view it could be split in two. Base management and army management.
In your case I’d pick the one in which you have the most interest.
If it’s base management, start putting down different building, make them spawn unit over time, add some ressource management, etc.
If it’s army management, start making them attack each other, add different types of unit with different abilities.
Whichever you pick, I’d say the important part is start small and make sure you achieve something in a relatively small timeframe so your motivation stay at its peak.
I would start with the top-down template. From there, break down the tasks you need to do. For example:
Spawn a cube/building that, in turn, spawns more units when you click on it.
Get your mouse interacting with the environment, so you can drag squares to select the units inside it.
Create a controller to get them to move where you click. (Here is a link for AI crowd behaviour from the incomparable Rama: Rama's Victory Game ~ Twitch-Reaction Multiplayer Co-op Action Platformer - Game Development - Unreal Engine Forums which will get you moving more than one unit around).
Create combat. Melee, then ranged. Melee can be fired by overlapping simple collisions and punching animation (see Epic’s own 3rd person series: null - YouTube), range by line tracing (See Tesla Dev’s Simple Line Trace clip here: Unreal Engine 4 Tutorial - Simple Line Trace Weapon - YouTube).
Spawn more buildings that change the combat stats of your units, or spawns different units.
Finally, try these videos, to go futher: https://www.youtube.com/results?search_query=unreal+engine+rts
As you can see, there are lots of people out there sharing their skills and ideas. Very cool.
That can form the backbone of the prototype. From then on, it’s tweaking and art and lots of hard work. 
Good luck!