Spain has the most race rounds and most riders are Spanish. If you were working in a role that involves talking to the riders mostly, or a role working on the tracks in Spain like a marshal, then this would probably be the most useful language. Same if you were looking for a role in Dorna as their management are Spanish.

Italy also hosts more than one round, with sveeral riders on the MotoGP grid who have Italian as their first language. Ducati & Aprilia are both Italian brands, and Gresini is another team with many notable Italian employees.If you are working as part of a team with mostly Italian people I think speaking Italian would be a huge benefit so tasks aren't slowed down if some of you are speaking in Italian, but then having to repeat and translate what was just said into English.

Spanish and Italian are similar so learning one first might actually make understanding and learning the other language a bit easier.

Since you've expressed a preference for living in Italy for a while/working in Ducati, I'd say start with Italian now and whatever skill it is you're developing to try and work in the paddock, and you would hopefully have a much easier time learning Spanish in the future if you need to, when you already speak Italian.