Map Strategy Question

[das123]

I'm still finding my feet with the depth of the game and have now tried a couple of 8 player games vs AI on Easy with a couple on Normal difficulty to see what happens.

My question relates to the initial random map placement. If you are located in the middle of the map do you try to build a defensible position around your starting fortress? Or do you fight for a corner and build a secondary defense base there?

I'm finding I can fight my way across the map against the Indies (not risking war with any other nations) and into defensible positions during the early part of the game, but once the mid part of the game starts I get attacked on many fronts because I have a long border with most other nations and the AI wants their piece.

I have been raising each province to between 15 and 45 PD depending on their importance to my overall plan but these can't hold out the AI in the mid game. Any suggestions on PD? It is costing me most of my income each turn.