Audacious

If you're going to use the audacious package opensuse provides, then you should install all of the dependencies it asks for, since opensuse built their audacious with those features. Generally, this will be easiest for you, though it will pull a lot of packages since opensuse probably enables most (if not all) of the optional features

If you're interested in building your own audacious, then the answer to your question depends on what features you want, what your distro names its packages, etc.
Generally, you get the audacious/audacious-plugins source, and use './configure --help' and clues from the resulting configure errors to figure out what build packages you need.

That doesn't really answer it in my opinion. The question is about "too many packages" for Audacious and its plug-ins to begin with. If the built software is stored in multiple packages, with some of them being optional, the user may choose which plug-ins to install. And as some plug-ins depend on additional libraries, their packages would pull in other packages as dependencies, which you cannot ignore if they are mandatory. Possibly some stuff that isn't desired. For example, if you don't listen to MOD music, you don't need to install a MOD plug-in with its dependencies, and you would not need to disable an installed MOD plug-in either.

It would be necessary to examine what packages openSUSE have created and what they consider optional. Look for base packages, which install the basic working player and extend it. Or install all Audacious packages you can find, if you don't mind the space requirements. Else you need to get familiar with them and install only those packages you really need.

The packages I get are these:

S | Name | Summary | Type
--+----------------------------------------------+------------------------------------------------------------------+----------- | audacious | Lightweight Audio Player forked off beep-media-player | package | audacious | Lightweight Audio Player forked off beep-media-player | srcpackage | audacious-debuginfo | Debug information for package audacious | package | audacious-debugsource | Debug sources for package audacious | package | audacious-devel | Development package for audacious | package | audacious-lang | Languages for package audacious | package | audacious-plugins | Plugins for Audacious | package | audacious-plugins | Plugins for Audacious | srcpackage | audacious-plugins-debuginfo | Debug information for package audacious-plugins | package | audacious-plugins-debugsource | Debug sources for package audacious-plugins | package | audacious-plugins-input-adplug | AdPlug input support for Audacious | package | audacious-plugins-input-adplug-debuginfo | Debug information for package audacious-plugins-input-adplug | package | audacious-plugins-input-fluidsynth | Fluidsynth input support for Audacious | package | audacious-plugins-input-fluidsynth-debuginfo | Debug information for package audacious-plugins-input-fluidsynth | package | audacious-plugins-input-sid | SID (C64 music) input support for Audacious | package | audacious-plugins-input-sid-debuginfo | Debug information for package audacious-plugins-input-sid | package | audacious-plugins-output-pulse | Pulseaudio Sound Daemon output support for Audacious | package | audacious-plugins-output-pulse-debuginfo | Debug information for package audacious-plugins-output-pulse | package | audacious-plugins-transport-http | HTTP and WebDAV protocol transport support for Audacious | package | audacious-plugins-transport-http-debuginfo | Debug information for package audacious-plugins-transport-http | package | audacious-plugins-transport-mms | MMS protocol transport support for Audacious | package | audacious-plugins-transport-mms-debuginfo | Debug information for package audacious-plugins-transport-mms | package | audacious-plugins-transport-smb | SMB protocol transport support for Audacious | package | audacious-plugins-transport-smb-debuginfo | Debug information for package audacious-plugins-transport-smb | package | audacious-xchat-plugin | Audacious Xchat2 plugin | package | conky-feature-audacious | Pseudo Package for conky with Audacious Support | package

I would appreciate if someone could give me a hand choosing the packages; by default the package manager only chooses four additional libraries when I try to install audacious.

Thanks.

That's really hard to read...

Not only is it really hard to read, it also contains a wild mix of -debuginfo packages, -debugsource packages and src.rpm packages.

Filter those out, and the list will be much shorter. ;) Typically, you don't need to install the -debuginfo packages as they are only relevant for debugging the software or when creating stack traces for problem reports, for example.

What's left? audacious, audacious-plugins, audacious-devel (needed when compiling software that uses the Audacious API), audacious-lang (translations apparently), audacious-plugins-input-adplug (read up on what AdPlug does), audacious-plugins-input-fluidsynth (read up on what Fluidsynth does), audacious-plugins-input-sid (for SID music), audacious-plugins-output-pulse (output to Pulse Audio), and a few Transport plug-ins: audacious-plugins-transport-http (certainly needed for streaming from HTTP servers e.g.), audacious-plugins-transport-mms, audacious-plugins-transport-smb, audacious-xchat-plugin, conky-feature-audacious (read up on what Conky is).

Oh, I'm sorry, I don't know why it appeared like that; while I was typing, it was a perfectly organized table. Anyway, I am researching what everything does and have a clearer idea of the packages I will need.

Thanks for your help.