Ok. First of all: normally you dont need Dreamup at all. It is just a tool for (rather seldom) emergency cases. Usually you can recover your box -if something really went wrong- by bringing it into "Stop-Mode" and flashing a fresh image with a web- browser. There is a wiki about this.

To access the dreambox from your computer i would suggest dcce2 (google for it) as it contains the components you usually need. To connect to the "backbone" of your box (the linux console) I would recommend putty (although this can be done with dcc as well, but not as comfortable).

I do not know, which plugins you need, as I do not know what you want to achieve...
There are tons of plugins out there and only listing them would last for hours...

I personally use:
Emc - enhanced movie center: a very comfortable replacement for the default movie list. Alternatively you can use ams (advanced media .. Something)
Autotimer: records every occurence of Navy Cis, Mentalist (for me), Biene Maja, Kleine Prinzessin, Simsalagrim (for my kids) automatically by just adding a search pattern...
Cool tv guide: a vers cool epg (one alternative would be merlin epg center)...
Dflash: make a complete backup of everything on my box before I start playing.... And restore if I break something...

And a lot more...
Plugins can be found on your box (software manager, depends on the firmware you are using what is in there), in forums or via google...

Just start playing around, and you will find your own favorites... No one can help you with that...