As you're using 4LLL, I shall assume you're using CFOP. However, as you're still fairly new, I would recommend looking at some of the other methods before you completely commit yourself to CFOP- at least just Roux, ZZ, Petrus and PCMS.
1) Try to learn most of PLL and start using a 3LLL. (only CFOP and ZZ)
2) Minimise any pauses you may have. Remember (quoting from a sig but I can't remember whose) slow is fluid and fluid is fast.
3) Make sure you can plan the entire cross/FB/EoLine/F2P in inspection and then solve it blindfolded.
4) Once you can do the above, try to track the pieces need for at least the first bit of the next step. Typically, this is the DR edge for Roux, the first pair for CFOP and whatever looks like it could make a good start to F2L in ZZ and the next few pairs in PCMS. Eventually you should be able to do this with the first step in inspections and solve the whole thing blindfolded though this is usually when you are sub-15 and probably verging on sub-10.
5) Factoring into the previous points, make sure your lookahead is very good and that there are only the tiniest, tiniest pauses that are <0.5 seconds where you decide what to do or recognise what alg you have to perform-slow solving is a really good way to practise this.
6) Minimise rotations. For Roux, ZZ and PCMS, there shouldn't really be any rotations though the whole solve. For CFOP, there should usually be none during cross (unless there is a
really good cross or Xcross or similar that is much easier to fingertrick), maybe 2-4 on average during F2L and 1 during LL (usually to get an AUFless PLL- rotations during algs don't count but you may want to find another alg if it has a roations in it that can't be performed another way such as L x as r).
7) Speaking of algs, when you select your algs, always make sure that you have the algs you can do or train yourself to do the fastest. Algdb.net is usually a good place to start and several prominent cubers also have their alg sets in links in their signatures or on their Youtube Channels.
8) Also on the YouTube channels, several of them will have tutorials that will help explain what you need for each speed from sub-60 down to sub-10 (I think pdf may even be making one for sub-8 Roux at some point).
9) Lastly, make sure you understand the cube on some level and can instinctively see how to build blocks or solve pairs without thought as this will especially help you to force nicer cases and find better solutions: partial edge control and multislotting are good examples of this in CFOP, misoriented centres, UL/UR pairing and partial CMLL partial edge control (CMLLPEC?) are good in Roux, ROLL wourks for both ZZ and CFOP and partial CO with LS in ZZ.
10) Have some kind of colour neutrality- x2,y is usually good for ZZ and Roux but try for full CN if you go with CFOP.
Sorry if this initiates some sort of text wall syndrome but I wanted to be thorough. I hope this helps and good luck with your progress and future efforts!
E: reading through your post again, I don't usually care much for hardware but you really should use something other than an actual Rubik's cube. A Thunderclap is a good options and it only costs around $8 last time I looked.