What's the best way to get resources?

That depends on which resource you are looking for. In your base you can produce a load of items that are essential for building upgrades and if you are short on items and need some right away you just need to use your rush speedup tickets.

You can also use the black market to purchase items using other resource items, usually the exchange makes this worthwhile.

You can get money, oil and steel by mining these items on the map.

Other items which are essential for unit upgrades you can get by playing through the campaign missions.

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