Depends what you want to do. You can couple it with Musescore (the program, not the web site - though that's useful as well), so if you can write music - or are willing to have a go, you can generate audio or Midi from Musescore, and import into lmms. You might want to work directly in LMMS though - it depends what your skills, experience and intentions are.
If you want to mix audio, then the current LMMS versions are limited - so you'd need a separate audio editor. Audacity seems to be the one which most recommend. There are a few other free ones, but Audacity has a long reputation for being good.
There are a few gotchas with using LMMS together with Audacity, and some people might want to do most of their mixing etc. in Audacity. Again, it depends what you want to do.
One other thing to watch for is which platform and OS you intend to use. I think - though haven't checked - that LMMS may work best on Windows. The other programs which I suggest to work with it should work fine on that. LInux is probably OK.
MacOS may present problems. Firstly finding a version of LMMS which works well with MacOS may take a bit of checking. There are two that I know of - one is much older (pre 2010) - the other is more recent.
If you want to use synthesised sounds LMMS has some decent capabilitieis built in. If you want to mix "orchestral" (really synthesised, but some like an orchestra or "real" instruments) sounds in as well you need the version which does sfz virtual instruments. You might have some luck with VSTs providing you don't "upgrade" MacOS beyond Mojave to Catalina - which just about kills everything, or any free VSTs you may have downloaded. I expect that in a few years time this situation will have changed, but if you have a version of LMMS (or any other DAW) which works with VSTS and AUs which were written before Mojave came out, then do not expect things to work well if migrating to Catalina. Probably best to do a complete system clone as a backup if trying that, or run Catalina only from an external drive.
Whether similar issues will eventually happen to Win PCs I can't say - as I've avoided Windows for years. Up to Catalina I would have said that MacOS had the edge over Windows - with quite a few problems and difficulties reported for Win10 - but it may now be easier to handle than MacOS+Catalina, or the next version of MacOS.
I also use other DAWs such as Logic and Reaper which have also been affected by the latest MacOS updates.
I should add that I looked at several other "free" DAWs and most are trial versions, and charges kick in after a while. Some are also incredibly awful to get installed or use. LMMS may be a bit quirky, but with a bit of perserverance you should be able to get it to work.
Reaper is another quite good choice - but you may find eventually you have to pay. Previous trial versions have not actually expired after the initial trial period, and I used it occasionally for over a year before I eventually decided it was worth paying for. That can also be tricky to get up and running and use, and you might need to look at many Youtube videos and tutorials to use that.
I recommend looking at videos and tutorials for LMMS too.
It may be that LMMS can indeed suit your needs. Do download Musescore, Audacity as well. Good luck.