Sell EC Points, buy food and stone, and trade generally to make money. You must also regulate your production by alternating production sites at home. The two wine producing hill areas are a case in point. When they are not producing wine, turn them over to horse or sheep farms. Alternate between arable and sheep farms on some of the B co-ordinates.
Flexibility is the key.
Aim to stock-pile food especially. If a would-be Spanish blitzkreig turns into a long drawn out siege, you will need it. If you are invaded, your enemy will look for a quick knock-out. If you can deny him that then you are half way to survival. At the start of the game, Spain and Portugal are roughly equal in strength.