Mega Man II/Air Man

Although it requires some platforming and unique enemies, Air Man's stage is a decent choice as the first stage to play. Although the level features many enemies unique to this level, the variety of the enemies are small and most are easy to avoid. There are clouds covering certain areas of the stage, which may be difficult to navigate through the stage smoothly on your first play. Additionally, the Scworms present throughout the level are very hard to avoid or defeat, since it is mainly out of range.

Stage
Make sure to shoot the eggs of Pipis before it hatches. They appear in a very predictable place and the eggs drop very slowly, so they are quite easy to avoid.

While jumping over the Goblin heads, jump slightly ahead to let the next head load before you jump. On the last jump to the platform, there is a Pipi blocking the jump. It is difficult to spot because of the cloud, so be aware before jumping.

Here, dropping through the bottom pathway will let you land straight onto the block on the 2nd image. After sliding through one of the two pathways, there is a large energy capsule on the right bottom, hidden by the clouds. However, it might be difficult to get through the Scworm after obtaining it, without getting hurt. One option is to keep shooting the spawning Scworms until it drops a energy capsule, and get hit while healing with it. If you are on full health, it might be easier to jump over it and skip the item.

Keep shooting the Pipis, and jump carefully between the Goblins. While Matasaburo is on the screen, Mega Man is pushed backwards and jumps become much harder. Quickly get rid of him before taking on Puti Goblins, or jump onto the next platform to skip them and safely avoid falling off. Kaminari Goro is not too challenging to defeat, as long as you move carefully. They always appear in the same position, and shooting them will let you jump on the cloud platforms. On the first jump, be patient and jump at a safe timing. Drop left if you want to skip the second Scworm. There is a gap behind the clouds on the next screen, so jump over it if you want to skip the last small robot of the level, before fighting Air Man! You can grind for items here, if you need extra health before the boss fight.

Air Man
Airman will shoot multiple patterns of gust three times while pushing Mega Man back, and jumps over to the other side of the screen and repeating the attack. The gust reflects Mega Man's bullets, so you can only damage Air Man while they are not blocking your way.

Slide or jump over the gust and keep shooting. The invincibility frames for the robot masters are very short in this game, so you should be able to damage it quickly. Air Man's weakness is Leaf Shield just like in the original Mega Man 2, but it is a little hard to hit him because of its large hitbox and the gusts, combined with the fast weapon energy consumption. Still, you can end the battle much faster.

After defeating Air Man, you obtain Air Shooter, which you can shoot upwards, and Rush Jet, one of the most useful items that can skip most challenges in the game if used correctly!