Arsenal is not used to buying expensive players from onset and I don't think that has changed. Gyokeres might end up staying in Sporting if no club is interested in paying such huge amount on him when there is no guarantee that he will score as many goals as possible when he is signed. Arsenal will prefer to go for a player with lesser amount but quality enough to play Gyokeres role as a striker.
Arsenal doesn't have many problems with their players because the players they already have are not bad, but I think Arsenal just needs a good striker. Having a good striker can change their struggles, as they have been trying to win the Premier League title for some time now. Arsenal doesn't spend much on signing players, but the players they have are not bad. It would be a significant advantage if Arsenal puts in a lot of effort to buy a good striker because this is what the club needs to improve its performance.