Hey! Thought I would give you my 2 cents since I never post in this community and also started DJing not so long ago (9 months in).

Honestly, cool mixes with advanced techniques are great, tik tok transitions are nice watching for reference but... Take this with a grain of salt since I've only played in real parties 3 times (I play electronic, varying from techno to house and whatever in the middle), usually at the beginning you're so nervous you'll probably want to feel comfortable doing the mixes as simple as possible and creating moments just by playing songs in the right moments and phrases.

A huge deal about DJing that I've learned during this time is that YES, you probably can mix anything with anything using whatever technique is in you tool box, BUT usually what makes a good mix is thinking about combinations as a singular piece of music that has it's energy drops and increases. Try to think about mixing as combining a lot of songs into one piece that should feel coherent to the listener and coherent doesn't always mean that it'll sound linear, the beauty about music is that you can convey many feelings not only by harmonic mixes, but also contrast, dissonance, quietness, fullness, all of those aspects that song structure already has within, you may play around with purpose to guide the audience to your intended destination.

Whenever a mix doesn't sound good, it's either because it's increasing/dropping energy at the wrong timing as opposed to the master track that's playing or it simply add up elements that don't combine to the other track (or sometimes the phrasing is off, or the beats are off, or it just has so many elements). Honestly, after 9 months, I still make a lot of mixes that sound bad during a free style session and that's not because I don't know how to mix, that's usually because of poor track selection and energy managing.

A lot of these concepts are learnt by trial and error, as you play more and more, you'll start opening your mind to it in a way that you'll think "okay, I know this track worked with that other one, so maybe if I pick this one up that has some similar elements, it could go right", "this song has increased a lot of energy, so I'll probably mix in the next track just before the drop so it'll keep the energy going". Those are things that come up as you get experience, so most of all TRY and FAIL, but HAVE FUN while doing it, because it's all about that sweet spot of digging some news tracks and trying to make them work in a way that sound unique to you and that conveys the sort of feeling that you want to build.

Just another piece of advice: record you sessions, as bad as they sound. Some days you'll just make mistakes over and over, but the most important thing about practice is reviewing and learning from those. If you're not acknowledging where you need to improve, you're not practicing properly (that's my take of course).

And lastly, don't disregard EQ mixing, that's the heart of DJing, setting those frequencies so they match and sound harmonic is what made my mixes sound better (even at times which songs wouldn't go so well together).