My car is a Honda Civic LX 2002, 4 cylinder. It is overheating after I've changed the thermostat, there are no cracks in the cylinder block and radiator, brand new gaskets.
There are a couple reasons for overheating.
System can't build pressure, so boiling point is lower. Could be a leak, bad radiator cap, or an air pocket. Look for visible leaks, they will eave a white residue behind. If it is the cap, you will likely not have pressure in the upper hose. Coolant overflow bottle may overflow. Not sure on the best way to determine air pockets, other than process of elimination.
Temperature goes up quickly. Heat works and helps cool the engine, but will likely not be enough to keep it in the operating range.
Could be partially clogged. Temperature increases slowly, especially under higher load. Heat helps bring it back down to normal. May be cold pots on the radiator. Both input and output hoses hot.
Fans don't come on. This will lead to overheating when you are stopped, but not when moving.
Little/no pressure in the top coolant hose. Top radiator hose also cold. Heat does not work.
Be aware, heat not working could also be a clogged heater core, or bad heater core valve.
Be aware that some vehicles require specific "set up" to properly fill the cooling system. For example, my 2001 Passat requires that the coolant overflow tank be loosened and raised, so that the tank becomes the highest point of the system; then, a specific hose must be loosened to make sure that no air remains in that hose. I don't know if your Honda is like this, but a look at a shop manual (or speaking to someone who knows the model) might be useful.
And while this isn't an answer, I'll ask: is the water pump operating correctly? The symptoms you report could be caused by a failed pump.