Great to hear about your newly discovered hobby! Sound designers are truly the scientists of the music and audio world and they lay the groundwork for music composers all over the world.
One of the most widely-used tools amongst sound designers (at least for me anyway) is their DAW. DAW's are excellent sound design environments jam packed full of all different kinds of effects such as delays, reverbs, modulations (chorus, phaser, etc), vocoders, and many more! Using these plugins that are already installed in your DAW, you can create insanely cool and unique effects racks that you can apply to any sound to create something amazing!
Some plugins that you may want to add to your DAW for sound design would be multi-band resonators, convolution reverbs, and frequency shifters (as well as ring modulators).
Convolution Reverb plugins work extremely well if you want to create atmospheric sound sources or just plain weird sounds!
There's also a wide-variety of dedicated sound design software out there that you could look into purchasing in the future, some include:
- U & I Software's MetaSynth (my personal favorite)
- Native Instruments' Reaktor
- 2CAudio's Kaleidoscope
- Symbolic Sound's Kyma X
When it comes down to it, sound design is all about experimenting with different combinations of effects and processing techniques; there's no "magic tool" when it comes to it. More often then not, the best sounds are often discovered by accident.
I hope I helped you out in anyway, and please, if you have any further questions I'd be more than happy to answer them for you :)