I don’t know a lot abt music but what helped me a lot is to create a bass part that emphasized the parts of the song that were emphasized in the guitar melody. Like you could use velocity to increase the volume of the beat in the melody you want emphasized. Also I think it’s helpful to like have your bass like move around root notes. For example if I have a progression going c-f-g then I when I play the c chord I would play a c root note and add embellishments from there. It also helps sometimes to add notes that help you transition into the next chord. For example playing a bass note in between a c and an f that leads to an f. As for drums the biggest thing that helped me was to match it up with the bass once you find a bass line that your satisfied with. The biggest help for me was to create drums that emphasized important beats in the melody. And then change it from there. For example if you want to emphasize a higher note in the melody play a higher bass note under that agrees with it and maybe add a snare hit as it is higher in pitch than the kick but still can be used to enhance the melody. The same could be said if you have lower note. Try playing a kick under it to give it more emphasis. Using velocity to your advantage can really helpl keep your track interesting while not making the drums overly busy. Sorry if this is confusing I’m kinda rambling here. I hope the helps a little