Hi Simmo,
And welcome to IIS
.
I agree with Scott,
especially about the height adjustable chair.
These can be bought from telescope shop for about $160. (Or you can make one yourself if you are that way inclined, I think there is a project on here about that).
Get yourself a red light head light, so you dont trip over your chair and you dont destroy your night vision.
A good peice of computer software to tell you what is about, is Stellarium. This is a FREE download, and a truly excellent program.
You will need some star charts. Personally I recommend a subscription to Australian Sky and Telescope, they have monthly star charts, and articles on items that are good in the sky each month (well 8 issues a year actually).
I prefer a Red Dot finder to a telrad. A bit easier to use and less complicated, while doing a similar job at less cost. This will get you in the right area of sky first, then use the finder scope to zero in. If your scope does not have a right angle finder, I suggest you will appreicate the investment to upgrade to one.
As Scott said, good collimation makes a big difference, so good collimation tools will be helpful.
If your climatice conditions are like here, Dew Amelioration will greatly extend your viewing time. Read up on this and discuss with experts. Typically, a secondary mirror dew heater, and a (home made or other) dew shield, will be a good start. Also, a lot of scopes come with a primary mirror cooling fan. These are good to get the mirror to ambient quickly, but some people recommend that they are useful to slow dewing also.
Good eyepieces can cost as much or more than your scope.
Although the ones coming with the scope will probably be OK for starters, you will probably like to upgrade at a good widefield eyepiece for most deep sky objects. Personally, my favourite such is a Televue Panoptic 27mm. This may be around $450.
If you want planetary views, higher magnification will be necessary. In this area, my experience has me going back to a Televue Nagler 9mm regularly. Probably around $300.
Now many will say you don't need all this stuff at the start, and that is true.
But you did ask specifically.
And most will say look through the varouis optional extras first and speak to others on their experiences, and this is good advice too.
Again, I am not saying you need all this, but in my experience, these are items I have found that have improved my viewing experience over time. And thats what you asked for.
BTW, if you are getting a collapsible DOB, first recommendation will be a shroud.