[Xrystal]

It should already be ignoring the other items.

Also, looking at your line for BuyMerchantItem - the wiki page doesn't say it returns a value, so it will always be false I suspect. This could be the cause of your problem
https://warcraft.wiki.gg/wiki/API_BuyMerchantItem

local function BuyItemsFromVendor(vendorName)
    --  Create a table of items for this vendor's name
    local vendor = vendors[vendorName]   
    -- No items ?  Then don't bother with the rest of the work
    if not vendor then return end               
 
    local numItems = GetMerchantNumItems()
    for i = numItems, 1, -1 do
        local name = GetMerchantItemInfo(i)
        -- Is this item in the list of items for this vendor we want to buy ?
        if vendor[name] then                      
            local success = BuyMerchantItem(i)
            if success then
                PrintMessage("Purchased: " .. name)
            else
                PrintMessage("Failed to purchase: " .. name)
            end
        end
    end
end