I've been playing assorted instruments since the mid 1970s (though violin for less than 2 yrs now, so I still consider myself a noob on it), and in my experience anything that gets you to pick up the instrument and dust it off and play is good.  It all helps, at least a little bit.  Same goes for any study of music theory, history, etc, even a little bit here and there is likely to be helpful eventually.

Practising improvising will *mostly* help you get better at improvising.. But some of what you develop on intonation and bowing, some of the transitions between notes you come up with while doing improvisation, will definitely also help other forms of playing.

Practising sight reading will *mostly* help you get better at playing from score, but you will get new ideas from those scores to use when you are improvising and get comfortable with some transitions between notes that you might not have thought of on your own.  And of course, your intonation and bowing can also improve from it.

Practising playing by ear will *mostly* help with being able to listen to a melody or musical phrase and just play it on your instrument.  But obviously some of what is learned while working on that will help with the other areas too.

All good stuff, and well worth the effort, in my opinion.  They are useful skills for making music, and the more you use them, the better your playing gets.

I personally prefer to play from memory.  I don't feel I have a piece down unless I can play it right off the top of my head, without any sheet or listening the piece through right before playing it.  I may learn the piece from a written score or from hearing it, but until I can play it through without errors with no "helps", I don't think of it as a piece I "know". 

I don't really work on elements like expression and dynamics until I have it to that point.  Then I take the song apart into sections or phrases, and listen to other people's versions and think about what I want it to sound like when I play it, and I practice it in sections, focussing on getting the sound and feel to be what I want.  Music is communication, it says something.  Getting to where I can play it without goofing up is just the start for me.  Then I work on getting each sound to have some meaning I want to convey.

When it comes to learning, we are all different.  Experimenting and trying different strategies to find out what actually works best for *you* is part of the process of effective learning.  We kind of have to "learn how to learn".

From what you are saying, rockinglr33, it sounds like you are finding improvisation to be an effective learning tool for you at this time.  So yeah, go with that, and use it to get yourself to play more, and get better.  Somewhere down the road, you may find other things that become more helpful to you and so you shift your focus to them or include them in your practice.  As you continue to learn, what helps may change a bit over time.  That is natural.

Now for getting better at something specific like sight reading, what I would probably do is this.. Take some piece that is simple enough that you can read it fairly easy.  It doesn't have to be "Mary had a little lamb" or "Twinkle twinkle".   It can be just a section of some classical or pop or whatever piece that you really like and want to be able to play eventually.  Most pieces, even advanced ones, have at least some sections that are pretty simple.  As little as a dozen notes can be enough to recognize and enjoy playing, at least a bit, so that would do nicely.  Play that through a few times every day while just following along on the score with your eyes.   Low pressure, easy bit, and you can spare a bit of attention to remember to relax and actually enjoy that bit you are working on.  Do that for a week or two, giving your brain some time to build the connections between the dots and the sounds and where the fingers have to go.

Then you try reading some other simple bit and see if it is easier than you feel it would have been before practising the first simple bit. If it definitely seemed to help, then you have a technique/method that you can use to improve the particular skill of sight reading.  If it doesn't seem to help, then you think of some other trick to try.

What works "best" tends to vary considerably, from one person to the next.  Find what works best for you at this time and then work the heck out of it. LOL