Hello and a warm welcome!
I think the others have already said what's to be said, but the most important step in choosing a telescope is to actually look through one, much like trying a set of clothes or shoes. And the only way you can do that in Singapore is to go to a sidewalk session.
Its very important because while you can definitely see a lot of objects in Singapore, the heavy light pollution does affect things to a great degree so by joining these sessions, you will get a good feel of what you can or cannot see through a particular scope, hence you will know how to spend those hundreds or thousands of hard-earned dollars
Regarding the various types of scopes, most decent quality scopes of the same size will produce fairly similar images so don't fret too much about their type unless you intend to do astro-pohotography.
Generally a refractor is the best all-rounder but comes at the cost of steepest price per aperture size.
A Cassegrain/SCT is compact, in the middle as far as pricing is concerned but sacrifices some optical quality compared to refractors (there's a lot of technical debate here, but I'll leave that for the technicians
Suffice to say that unless you're quite discerning, you'll probably not really notice, or not notice enough to mind). Having said that, the cheaper cost per size of aperture allows you to buy, for the same price, a bigger Cassegrain compared to Refractor, and that bigger scope will usually show a better image.
A true reflector, such as a Newtonian or Dobsonian is the cheapest per size of aperture but will require some skills in collimating and maintaining collimation. Not as hard as it sounds but it will require a bit of work and extra knowledge as you set up.
Buying 2nd hand is a great idea as it means that should you upgrade or sell out, your loss will be much less as compared to first hand.