yeah I'm going to go ahead and give you a useful reply.
- Read build guides. Stay on meta until you are very comfortable making slight tweaks based on preference and build style.
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1963299164/33524117?tab=overview
BotRK is mandatory on Vayne. Not after PD, not after whatever you were using BF Sword for.
You can look at guides on mobafire, that's a good starting point, problem is that it those are often written by plat noobs like myself. Better to compare builds on probuilds.
http://www.probuilds.net/champions/Vayne
http://www.probuilds.net/champions/Vi
if it's an item that lots of pros get, like 90% of them, then consider it a core item on that champ.
Also idk why you get homeguards on everyone, that's kind of a situational item or even a 7th item.
.2. Get coaching.
Best to get coaching from someone two leagues above you (gold for bronze, plat for silver, diamond for gold etc) so find a plat Vi main and hit them up for tips.
.3. Watch streamers. Especially the ones who will commentate on what they're doing (a teaching streamer not a glory streamer) so you can get deeper into the theory behind their builds.
.4. Experiment with other champs in your favorite role. This way you might find a champ even more op and even not you understand them and their powerspikes/weaknesses better when facing them.
.5. If you are a jungler, ignore top lane completely and focus only mid, bot, and counter-jungling. Just tell your top lane first that they're on their own.