If you are going to join a corporation, specializing is required and most appropriate because you have a staff of fellow members who do the things you can't.

If you intend to make your own corp as Ralph suggests with additional accounts, then you should specializeeach account.

If your not going to join a corp, then you can generalize.

The downside to putting in EP as needed is a very slow progression. But it can also be very fulfilling to mine, manufactor, and blow up your own equipment.

If your going to try to compete on the market, or with production, then you will need to specialize, and run lots of hauling assignments to build up your initial capital before you can make NIC on selling items.

First of all, you wont get a bot with 4 industrial slots. You will get a combat bot which is able to use only two mining modules.

Transport missions are good for fast gaining of reputation which helps in manufacturing, but if you dont have access to the free movement on beta island (neutral bots being destroyed without any warning) this have no future. So try mining, its profitable too. Just buy an Argano and do some mining missions to know where is what to mine and gain extra credits on it.

About EP: If you're going to mine you're gonna need a Termis, this mech requires lots of skills for comfortable and efficient operating. You need to train skills to increase your capacitor, recharge and skills which reducing power cost of your medium mining modules. And dont forget to train skills which unlock this Termis for use.

UPD: You can craft whatever you want even right now, like light bots or ammo, such thing allways on demand. You just need an example of what you're going to craft and a decoder. But you will lose many materials, so train skills to increase factory minerals efficiency and gain reputation doing mining or transport missions.

Good luck.