What you have is the same as my first serious telescope after years of cheap ( all I could afford ) telescopes and was amazed at the quality of the views for the price so if I were you I would save my money and enjoy what these scopes are capable of .
First up a 2x Barlow from Bintel . Then some Supervue,s from either Andrews or Bintel , full set starting with the 15mm and then a 2nd hand 2inch diagonal from the classifieds here too use the larger 2 inch SV,s .
Just take your time and get these things one at a time and it won't be long until you have a better ( what you have now is a great start ) observing set up.
Yes. Barlow first then the 1 1/4 SV,s , 2 inch diagonal then to. 2 inch SV,s
,it doesn't take long.
Brian.