Need Bong Advice

How much money are you looking at? Thats the biggest question. With over about 50 I would say you could get a sweet percolated bong but it all depends on how much dough your willing to throw down.

 

it really depends on what you want, and how your gonna buy or order it.   personally my least expensive full sized tube was about 350, but its a DG fritted disc tube which isnt exactly a cheap brand. (well i do have one that was more like 200, but its an old school rubber gromet style piece that i only keep around for memories because someone bought it for me 10 years ago, havent even had water in it for years, much less hit it)
 
if you are ok with ordering online you can get a good deal on a quality piece from apix, more like 150 for a basic clear full size stemline from his site.  his stuff is high quality but he isnt a big company or a huge name brand yet, so the price is alot better for what you get compared to stuff from some of the big names in high end glass.

 

Buy a $15 acrylic single perc and spend the rest on weed.

 

I would buy a good old glass bong but that's just personal preference

 

Tough to say, it's all personal preference.  Some like more airy, more diffuse hits, and some like more chug, denser milk hits.  Some folks like big tubes, some like little ones.  
 
Name brand is one thing that affects the cost.  Sovereignty, Mothership, Toro, Olympic, etc will cost more just because of the name.  The type of glass used (simax or duran schott are very good glass).  The thickness of a piece (3mm vs 5mm vs 7mm glass).  Any kind of color work and you'll pay significantly more.  The desirability of a piece has a strong correlation with price, ie mothership fab eggs and sg pillars can be harder to find and command higher prices...of course if you ever need to sell your glass, these pieces hold up value better than stuff like ZOB or SYN.
 
100 is tough for a new bong.  You're not going to see many pieces at that price, even glass on glass bubblers are usually more. 2-300 bucks is a usual price for a full size tube with a basic perc.  You can look around for used pieces, plenty of people out there who are constantly looking to sell their older pieces to buy new ones.  Craigslist sometimes has some glass waterpipes, nuggetry has a classified section, etc.
 
There's another market but you need an invite plus 10 bucks or the membership is around 50 bucks, so if you're just trying to find 1 100 dollar tube, it's not really worth it to get membership.