How many people here generally buy used?

Both. Used when ever possible. but some times, new technology and outstanding products are not available used (for years).
KNOWLEDGE + PATIENCE+ OPPORTUNITY + FAST ACTION = VALUE. Have bought  both new and used with this formula and sold from 1 month to 30 years later and recovered between 55% and 115% of what it cost. IE. bought new speakers for $7500, sold in 5.5 years for $7000; 
amp/preamp new at $800 & sold 15 years later at $700; other speakers new at $1,000 sold 30 years later at $800. 
All current system components both new and  used cost 62% of their retail price. Only the preamp and speakers were bought new... used just do not exist (yet). The pre was significantly discounted because it was a discontinued model, but still, no used to be found. 

If you select (target) wisely, sometimes you also just get lucky. I have found some sellers care very little about getting top dollar  or “what it is really worth if you have patience in finding a buyer who really wants it”...they just want it gone... fast... no hassles. Getting a great deal on great equipment is like finding a fantastic bottle of wine at an unbelievably low cost. It’s SO enjoyable! 

Classic equipment purchased used including Fisher 400 & 500 receivers, McIntosh MR67 and Kenwood 5700 tuners, a pair of Yamaha CR620s, pair of Yamaha 200 amps, all my speakers-Legacy Focus, Legacy Signature IIIs, ADS L620, Dynaco A-30, A-50, McIntosh mx110, Fisher 400cx I’ve sold half of the electronics already.

All my other equipment was purchased new.

I spent many years buying and selling used gear, figuring out my sonic preferences while living within my means. More recently moved to working directly with small boutique manufacturers to obtain new gear that gets me really close to what sounds best to my ears. At this point only my Ayre power conditioner is used, the rest was purchased new directly from the manufacturer (which, without markup, provides the price-performance ratio of used WITH warranty and post sale support) or from excellent dealers who will work with me on price.

I’ll buy both new and used. I try to always to find used first. Amp used only 6 months old when I purchased it. Speakers were open box. Turntable was a demo but I also got a great trade in for an integrated amp. Essentially resulted in a new, free phono cartridge. Phono preamp new on sale.  DAC new. CD player new but on sale. Preamp new but I got a good trade in for my old preamp. I have not yet been able to find the preamp I purchased on the used market and it’s been about a year.

My current system is a mix of new and used. My newest piece is a dac, bought 3 months ago. My oldest piece is a 25 year old tube preamp, bought used several years ago. Couldn't have afforded it if new. Bought amp, sub, and turntable used, speakers and CD transport new. My only Chinese built component is the dac.It is excellent,however it will  be my last new made in China component for obvious reasons(regime, not the people).The rest is mainly U.S. and U.K. 
    No hard fast rules on new or used., just what is best at time of purchase.