You need 3 dynamo, hardened energy conduits and at least a redstone battery.
You will overall use less then 1 dynamo unless you start to automated around. But it will sometime use burst of energy. Say you want to empty a chest in one go... That's why you need a battery and more dynamos ready. The last thing you want is to empty your battery and figure out that 1 dynamo is not enough to open your only inventory system anymore. Don't wait to lose access to all your ores before you build that 2nd and 3rd dynamo. Also make sure you have an emergency fuel source outside of the ME system.
Once you have this, you can also plug TE machines on the power grid.