What can I expect to see well?

As a beginner with a relatively cheap 500mmx114mm (f4.3) newtonian, what am I
likely to be able to see well?

The optics seem pretty good, though with the 2 eyepieces I have (17 and 10mm
plossl's), the top magnification I can get it 50x :-(

Now I do have a 2x Barlow, and a 4mm Plossl arriving soon, which will give me a
a range of magnifications of 29x, 50x, 125x, (and 58x, 100x, and 250x with the
barlow). I know this 250x exceeds the 228 theoretical limit, but I'm hoping it
will give a reasonable view of some things... I probably should have got a 6mm
instead, but hey ho, I'm just starting out, and I get to keep the lenses if I
sell the scope...

Am I going to need filters to see nebulae? What magnification is best to get
good views of jupiter and pluto?

I think I'm more interested in the nebulae + galaxy type observations, is that
what are called 'deep-sky obects'?

Thanks all for your input - and please look out for my other thread regarding my
next scope purchase!!!

Cheers,

CandT