Smallest Magnetic Relay and how to choose the Ampere rating
Solid-State Relays (SSRs) will be your best option for what you are trying to achieve here.  With a small external voltage source (3.3VDC - 5VDC), you will be able to switch a load with higher power consumption such as what you will be running at 230VAC.  

Below is a representation of how it will work and how you are able to switch to a load with high power consumption:



This works like an opto-isolator to keep your 230VAC away from your control circuitry.  

In terms of current (ampere), you will have to look at the current being drawn from your appliances and make a clear decision which relay would work best.  Light bulbs will have a power rating (30, 40, 60 Watts for example).  You must calculate the current drawn by each load by dividing the power by its operating voltage.  Simple for direct current.  A little more complex for alternating current.