Is this your first account? If so, you should be just generally gathering any set of general tips someone can actually give you for the game, because just that alone gets you to Gold.
Get proper runes. They need to all be T3.
Find at least 2 champions for each role you will main, primarily ones that don't get banned often. It's okay to have one that gets banned here and there, but that also means you will not be primarily playing it and will know less. Stick to 2 roles and be prepared to dodge if you are autofilled. Otherwise have a pocket pick for if you get autofilled. Try to not pick things that are hard to play mechanically or you won't be able to notice where you could've changed play patterns in your own spectates. In your case you picked Orianna so that's fine for now.
-Play a lot of games so that there's actual data on what you're actually doing. You've only just started.
-Focus more on CS rather than fighting champions. It's alright to make trades if it won't aggro minions (only AA's do this) and it won't push the wave too much. If your jungler is preparing for a gank, you should try to let the enemy push and then wait for your chance to CC them. Your jungler will follow up from there (but not always since it is based on range and type of jungler). This is advice that holds true regardless of matchup or the champion you are playing.
-Stay in "safe zones" where the enemy can't hit you with an AA without aggro'ing minions. Obviously try to dodge skillshots.
-Do not try to save teammates that will probably die before you get there and ignore pings unless you think the play will go WELL. You should not let your team decide where you should be going to help them unless you need to secure Baron (with the enemy jungler or multiple people on the enemy team dead while you have someone who can tank) or Dragon.
-Losing Dragon is not the end of the world, especially if it's an Ocean one. Elder Dragon is a different story.
-Try to predict where the enemy jungler is and place a ward accordingly. Play around that side. A jungler will typically start one side, finish on the other, then gank. Knowing where they start can help you as a mid laner immensely if you keep that in mind. An advanced observation you can make is checking jungle CS to see what camps he has cleared once he comes into vision, so you'll be able to do the math on where he is most likely to go if he has gotten done with a gank or failed a gank. You'd have to know the jungler's sustain off-hand though, so it'll take time for that.
-Check minimap often.
Watch videos of the champions you want to main for said roles (they must be around diamond+ elo so you can see what they're doing that you are not doing). If you intend on jungling then watching videos will help even more on the ones you want to play, because it will show you what camps they usually clear and how they perform ganks (be sure to check the date it was uploaded, as it can be outdated in some aspects). Check winrates if you'd like but don't let that discourage you from playing the champion. Notice if the champion roamed, who s/he is fighting and how s/he plays in that matchup, build paths/runes/skill level order/summoner spells, how they manage the creep wave, ward placement and timing, how often they check the map, how they pinged (unless it's passive aggressive), when they backed (which is usually if they have been chunked out or if they pushed the creep wave intentionally to buy themselves time), and teamfighting (position and when they use ultimate, also retreating).
After you learn all of that (yes it is a lot), you can ask for more specific tips. Most people in Silver like myself do not have all of what I mentioned refined to the degree that they can be consistent. It will get you to Gold just off of that stuff alone.