I'm really new to Pd and I wonder how much stuff is it capable of doing sound-wise without having to use other software

Miller Puckette offers his video lectures from his classes with Pure Data at UCSD for free on his website, here are the links,

http://msp.ucsd.edu/media/

"In this directory are recordings of classes I've taught at UCSD since about 2012, with some repetitions.

The directories are named by course number and date, so that "206.16w" means "Music 206, 2016, winter quarter". You can find corresponding syllabi and other course materials, in, for instance, ../syllabi/206.16w relative to this directory.
Of particular interest are the seminars, course number number 206, which are all different:

206.12f Real-time computer music software design 206.15w Feedback and distortion 206.15f Stored and live control streams for real-time electronic music 206.18s Frequency-domain audio techniques 206.19s The voice as musical instrument 206.20s Inside Pure Data

In addition to all those, various presentation and lectures are collected in the subdirectory "talks", and recordings of musical

I had tried to learn Pd several times since the late 90s but it finally clicked and i have been obsessed.

some of the things that have really helped me this time are YouTube tutorials...

Dr Andrew Brown's 65-part tutorial series is excellent for newbies, highly recommended..

https://www.youtube.com/watch?v=SLx7kjuFheY&list=PLuxj2jXSuTvvqYcDLJ-poN-JxvqX0wq-m

following these left me with the knowledge, and something of a toolkit, to be able to get satisfying-enough results to keep me motivated and excited, and the gears turning