The sound card choice is really a tough topic, especially for such a wide time range. I'll try to explain what I know and others will perhaps correct me if I'm wrong somewhere.
In the early era of DOS gaming there were these sound/music options:
- PC Speaker (mostly bleeps and tweets, but some games were squeezing PCM out of it - check Doom2D for example)
- Covox and relatives like Disney Sound Source (only suitable for PCM sound)
- Creative Music System (Game Blaster card, but also available as add-on chips for Sound Blaster 1.0, 1.5, 2.0 and ATI Stereo F/X (Stereo F/X CD, VGA Stereo F/X))
- OPL2-based cards (Adlib, Sound Blaster 1.0, 1.5, 2.0; multiple clones of Adlib and Sound Blaster)
- some external and internal music synthesizers that were supported by a narrow range of games (some Casio external synths, Yamaha FB-01, IBM Music Feature card...)
- widely supported Roland MT-32 (and its relatives CM-32L, CM-64, CM-500 and LAPC-I)
For PCM sound, SB and its compatibles or Covox/DSS must be used.
All this stuff (except for PC Speaker) costs a lot because of its extinction. If you plan to spend $100 on a whole PC, forget about this era of sound. You might get a cheap soundcard of later period though, that will be pretty compatible with early DOS era standards.
As sound producing techniques evolved, the next options appeared in the first half of 90's:
- Yamaha OPL3-based solutions, of which Sound Blaster Pro 2 and Sound Blaster 16 are the most known;
- a multitude General MIDI-compatible wavetable cards, daughterboards and external devices (of which Roland SC-55 and Yamaha MU-10 are perhaps the most known ones).
- General MIDI-incompatible wavetable cards, like Sound Blaster AWE32/AWE64 or Gravis Ultrasound.
As for PCM, this period demands having a Sound Blaster 16 or later (32/64). There were other cards that supported 16-bit PCM output (among them Gravis Ultrasound, Roland RAP-10, Microsoft WSS, MediaVision ProAudioSpectrum 16), but they were supported by a minority of games.
Most of these are expensive either. But it is possible to find a cheap Sound Blaster 16 or even an AWE32. Also you could go for less known soundcards like Yamaha OPL3SAx series. This one has an OPL3 chip which is backwards compatible with an OPL2 (thus you get covered the earlier era pretty well), and is compatible with Sound Blaster Pro standard.
The other inexpensive but rare option: there is a family of Aztech cards that are SB compatible, and are capable of emulating Covox/DSS. You will find more information about it here at Vogons.
The other inexpensive but rare card is Orchid Soundwave 32, which has its own wavetable and has a not-so-bad MT-32 emulation.
In the later half of 90s MIDI game music slowly extincted from production, being displaced by CD Audio and pure compressed and uncompressed PCM, like WAV, MP3 and OGG. But sound cards competed with sound positioning techniques, of which EAX and A3D were widely supported by games. For the first, you need a SB Live!, Audigy or Audigy2 card, for the latest - an Aureal Vortex-based card, like notorious Diamond MX300. They shouldn't be expensive.
If you aren't going to investigate this theme any further and don't want to spend much money, I'd say get yourself:
- an early ISA non-PnP SB16 CT1740 for an early DOS era ($15)
- an ISA PnP AWE64 card for the late DOS era ($15)
- a PCI Audigy 2 ZS card for Windows era ($10)