unfortunately in the current meta game your build might not work. You will be laning with a supporter who will have heal e.g. Astral Blessing so there is no reason for you to take Heal. Instead Exhaust or Ignite is the btter choice (personally I prefer Exhaust).

Also you will be last hitting as a carry so there isn't really a point in taking Vampiric Scepter. Instead Doran's Blade is the better choice as it offers a small amount of life steal, attack damage (makes last hitting easier) and 100 hp (vayne like you said is squishy).

Based on your item build you will nto be having boots. Bad idea. Vayne has very little range compared to other ad ranged carries. Thus she relies on positioning herself to deal damage using Tumble and her boots. Having no boots exposes you to a lot of damage and this is very dangerous as you have low movement speed and cannot escape easily. Vayne also does not realyl need to many armour penetration items. The reason being she deals true damage with her Silver Bolts. Hence it is better to get attack speed items like Phantom Dancer to trigger the third hit more quickly.

As for masteries, MR isn't going to be helpful on you. Early game the main source of damage you receive is physical attack damage from the enemy carry hence armour is the better choice. You won't face magic damage until team fights and even by then, an AP caster can burst you down quickly even with 6 MR bonus from your mastery. Hence you might as well make the most out of your early game.

Also I recommend reading jhoijhoi's guide on how to make a guide. She provides some insightful information on how to write a good guide.