Moneybase will allow you to buy securities in a currency other than that which you may currently have in your wallet as long as the total value of the order (when converted) is less than or equal to the value of cash available.
For example, you can buy securities denominated and traded in USD even if you only have Euro on your account.
We always recommend investors to exchange any funds required for trading prior to executing orders in other currencies to ensure they have the adequate amounts in that currency available to cover their purchases.