This could easily be "when this enters or leaves the battlefield, create ONE token." Reduce it to a reasonable power level and spread it out a little bit

Is that three 2/2s for four mana PLUS the haste-y blitzed 2/2 body of this?

­ is a bit of a high investment, if all you get out of it is haste. Usually a crew cost is less power than the Vehicle's power. Another option would be evasion or additional effects dependent on attacking (e. g. sabotage).

Why do I tap 4 power worth of creatures to attack with 4 power worth of Vehicle?

I haven't even talked about it before, but now that the equip cost is zero: Equip costs can be paid multiple times a turn to move around an Equipment. If you control this and five untapped creatures, you can reduce a player's life total by 20 life without any further investment - and if you survive another turn cycle, you can do so again. And I'm not even counting the removal option which will really help with that.

This design is in no way a common, but the equip cost just pushes it further. It's not even reasonable as a mythic.

Why does a four-mana Equipment allow you to repeatedly (not to mention again multiple times a turn) do as much damage as a four-mana spell that's used up after one use?

Look up the above-mentioned Heavy Arbalest, and you'll see in just how many ways this card upstages it.

You can write this as an activated ability with "Any player may activate this ability."

Problematic with tokens, which most Treasures are.

• Pay 0 with zero Treasure tokens, take your Treasure token.
• Repeat five times.
• Take your 5-drop with these five Treasure tokens of mine.

Really a Memnite is just annoying with this - might as well not exist. At the very least this wold need an additionally generic mana cost or be sorcery speed just to avoid stupid races for 0-mv permanents.

The activated ability alone pushes this past common or even uncommon.

Compare your card with e. g. Heavy Arbalest, Throwing Knife, Wolfhunter's Quiver.

This card gives you a Ninja's Kunai-plus every turn in addition to +2/+0 snd reach (which are irrelevant most of the time because you get to cast Flame Lash every turn - representing a 5-turn clock that can't be blocked and stays on board past creature removal, and is removal for mid-sized creatures as well.

This card isn't just "to good for common", it's "too much for a card". Might not need Aladdin's Ring costs, but anything repeatedly putting out 4 damage to an target is rare+ even after balancing.

It is much easier to parse your cards if you write triggered abilities starting with the condition: "Whenever a creature you control deals damage to a player, you may discard a card. If you do, draw a card."

Note also that I moved the discard first since this card has red, but no blue - and red gets to do rummaging with tthe discard first.

You can copy the rules text almost exactly from Scuttletide for the static ability: "Creatures you control get +1/+1 as long as there are four or more card types among cards in your graveyard." You could even use the ability word delirium!

I personally prefer to order ability word conditions the way Dragon’s Rage Channeler: "As long as there are four or more card types among cards in your graveyard, creatures you control get +1/+1." Having the condition first helps to decide early whether to consider the rest of the effect - but ability words can take part of that responsibility.

Both methods are valid though.

I feel Gangster doesn't really need to be a new creature type. We have e. g. Rogues.