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.