Khyber here's some advice for you:
1) learn the the basic meta
as in how the lanes are usually set ups and what roles most champions usually go.
the lanes are usually set up as follows: top - solo, jungle, mid - ap, bot - ranged ad carry + support
for the roles i will list them for the champions you have selected.
fiora: solo top, kogmaw: ad carry bot, lux: ap mid
of course there are many ways each champion can be played but it is useful to know what roles they usually are placed as in games. playing draft mode rather than blind pick will help you deepen your understanding of champion matchups and roles further.
# 1 is the easiest thing to do. here comes something a little more difficult
2) basic mechanics
mechanics is your ability to execute certain "feats" in the game. whenever you see someone make an amazing play or do something incredible in general it is usually due in part to their fantastic mechanics.
the most basic thing yet also the most important skill you need to polish is your CS-ing skills aka last-hitting (CS stands for creep score - ie how much creeps you can kill, this is a term carried over from LoL's predecessor DOTA)
if you wish to practice it is simple, go into a game with any champion at all and, without buying items practice last-hitting, that is only hitting a minion once in order to secure the kill. this is important for several reasons (it doesn't push the lane [if u push the lane you will be vulnerable to ganks,etc.], it allows for a steady and reliable way to farm early-mid game and for a few other reasons that aren't as important for our purposes).
this is a skill that can only be practiced by playing many games and can only be improved specifically if you have mastered the previous 2 skills. good players won't even have to stare at the middle of their screen to cs or to fight champions, in fact they will be most often glancing at their minimaps. the way they do this is through experience and habit. this can only be improved with much habit and by forcing yourself to look at the minimap as often as possible.
insight is like map awareness in that you need a ton of experience and practice to hone it. this is probably the hardest thing for anyone to learn. insight is your ability to foretell the outcome of a situation- ie if me and that guy fought right now who would win? if our team and their team fought who would win? where should i position my champion to do the most damage while receiving the leash amount of damage? if we do dragon can we secure it? is it a good time to do baron now? and many many more.
all these scenarios are handled through experience and understanding of the game which i title as being insight. this is the most difficult part of LoL and can only be done by playing the game.
so 1 is easy to learn 2 you need to sit down, think about and practice 3 comes with experience and 4 requires you to not only be very intelligent but also have perfected skills 1,2,3.
if you want to know more you can ask me.