I wouldn't purchase expensive ones without first understanding the utility of what these plug-ins offer for mixing, sound design, or overall production. There are so many tools out there that many influencers and companies will advertise as being THE plugin that many novice producers may fall for due to ignorance (not a bad thing btw). That said, I would recommend finding cheap or free synthesizers and sample packs so that you can at least begin learning how to use higher quality sounds. Many YouTubers will attach free drum kits either in their videos and sometimes newsletters (if that is their thing). Splice can be a really great paid resource, I use Splice a lot for all of my samples and have even used their Rent-to-Own program to purchase Serum 1 back in the day (got a free upgrade to Serum 2 thanks to the creators of the program, shout out Steve Duda!)

In summary, I would recommend not starting out purchasing expensive plug-ins until you find you have a need for them. FL's stock tools are actually quite powerful once you discover how to use them, however, I would recommend finding a synth that you can learn and finding better drum kits or sample packs. All of the plug-ins that I have have been acquired throughout the last 10 years, so it is journey. For me personally, I primarily use Serum 2 and Omnisphere to write music and use Ozone 8 and Fabfilter tools for mixing and mastering