If you cannot use cheats or ROM hacks (e.g., playing on a real Game Boy Advance cartridge), you can simulate a 2x multiplier by changing where you train.
Pokémon received from another trainer (via trade) gain 50% more experience in every battle. Lucky Egg (1.5x Boost): pokemon fire red exp multiplier x2
With double experience active, your progression through the Kanto region changes dramatically. Here is what to expect at key milestones: If you cannot use cheats or ROM hacks (e
Running walk-through-walls or infinite money cheats alongside EXP modifiers can cause memory conflicts. Try running the EXP code completely on its own. pokemon fire red exp multiplier x2