Suggestion
I've got a suggestion for the store.
What if you were able to set item priority? Like if you are unable to purchase an item and you right click it it'll place a number starting with one and continuing up. If I want to but Aether Wisp I could click amplifying tome and set it to one and set wisp to two and every time I back to the store it'll automatically purchase what you are able to purchase based on your item purchase preference. If I had 600 gold it'll auto buy tome and if I had 900 it'll just buy wisp.
Of course, there's a slight flaw such as what if you want to change what yoy want to buy after the store all ready auto bought it, but that can be fixed by the undo button which can be set to also cancel all preferences set before the undo.