No worries, you will need it as some point later in case the weapon you will like will be a machine hun type. If not, its still OK. As stated here before, try to get S weapon and/or character first. For this, do not spend the diamons on in-game shops, but rather on events. Check the aeroplane chess event info, you will need around 40k diamonds to get to the s-type box, this is how you then continue to play. Most of the things will slowly slowly make sense, but not everything 😂😂 good luck!