Hi, i just started to play this game and i have a lvl 16 fighter. Right now i am doing some Sissirat runs on insane using the sissirat fighter strat, getting some good cash wich been spending on getting new ranks of the spells i use for that runs.

The thing is that i feel kinda stuck i have no idea what else i can do after i am done with this.. its getting boring cuz the xp is very slow. Any idea what i should do next?

After you dispatch Sissirat and his lackeys, the boss door behind him opens. You will find a one-way portal there that leads to Algor's Terror Dome (level 10-25), a new dungeon. When you outlevel that one too, you can find a portal to another one either on level 5 of that dungeon, or on the boss' level, after you kill him and so on.

Also, there is loads of quests and not all get's finished in one dungeon 1 to 7 run so one thing I like to do is to redo the dungeon on a higher difficulty.

You should get the map (made by JoeB) to see where you can go, and what level-caps the different dungeons have. You can find it here.
TheTownstons have more up-to-date maps (not much difference though) found here, but those aren't in one downloadable file. Good to check out though.