Grabbing PUs over nations that don't colonize is probably the best way to avoid it. If you've got Castilla under your PU, you're going to need to REALLY colonize, I bet. (Or try hard and blob over France or Italy, if you're Aragón.)
The reason for my transport issues is I was trying to put 3,000 men on one cog. I a noob so or course I have to ask questions. Besides claiming thrown what are other ways to get Caus Belli? Proclaim guarantee can get you one, but how directly can you get one.
That explains it ^_^
(Figured you would have noticed the 'this fleet can transport 1 regiment' note at the bottom ^_^)
Obscure Documents is by far the easiest way to get a CB out of nothingness; if you're Christian (I think) and it's before 1650 then you get a Holy War CB against everyone who's not in your religion group (and the Deus Vult NI gives one against heretics too), and if you're an Absolute Monarchy you get an Imperialism CB against literally everyone.
AFAIK those are the only ones that let you directly get a CB on a strong, developed nation without any real setup. After that, you can get a Colonial Conquest one against 'primitives' (which I assume means nations in the African or New World tech groups), and a Colonialism one against any nation that has colonies bordering yours. Dishonourable Scum is useful for helping the AI dogpile a blob, but using it without AI help probably requires you to be really powerful already (or get lucky and have a really small nation blob to a size that's still smaller than you).
The next easiest ones are probably guaranteeing or Sphere of Influence-ing a nation you know the nation you're targeting wants to attack. Sphere of Influence gives you a CB against any nation that has any diplomatic interaction with the SoI-ed nation, but it costs you 10 prestige to bring a nation under your SoI and they have to be significantly weaker than you both economically and militarily (and within a range determined by your current Prestige).
You can also get lucky and get missions that give you Conquest (to take a specific province) or Subjugation (to outright vassalize a nation) CBs.
The hardest ones to use are probably Alliance (you have to have an alliance with someone who had an alliance with someone else that got attacked by the nation you want to attack (enh)) and Reconquest (which requires you to have core on a province they own). Diplomatic Insult is also pretty hard, since it requires the AI to insult you of their own volition (or get a random event that gives you one).
I
think that's all the CBs there are.