Friend, you need to focus on your economic pillars that can boost your naval capabilities in turn. Start with specializing in niche industries that can bring business back into Philippines and therefore increase your economic profile.
In terms of immediate defence, you guys should adopt a strategy that Vietnam has used so far; small but ruthless defence.
Have more of simple missile boats in large numbers that are armed to teeth and can damage ships in numbers. These are cheap to operate and maintain and provide a strong defence. In terms of aerial defence, you need to upgrade your air force radically.
Since your focus will be coastal and territorial defence, you guys should consider gunships rather than fixed wing fighters for now, or at the max something like EMB-314 Super Tucano, a proven platform against ground attacks. These are prop aircraft but can provide strong defence.
Rather than going for tanks, go for agile IFVs and APCs. To further make your job easier, you need to enhance your dependence on cheaper missiles in numbers, which will further save you $$ which would otherwise go in maintaining a heavy tactical platform arsenal.