10 Gallon Tank With 1 Platy. What Else?

[doraemon213]

Hello,
 
I have a 10 gallon tank with
 
1 assorted platy
2 live plants
1 driftwood
 
...and 1 black ghost knife, which I am going to return to the fish store as I won't be able upgrade to a tank size anywhere close one that is big enough to house him (I really really like him since I have started hand-feeding him very early on 

). Once that is done, only 1 lonely platy will be left since all others have died during fish-in cycle (all these beginner mistakes 

).
 
So, what kind of fish would you suggest adding to the tank? I really like colorful fish and having variety (although I know it is very limited in a 10 gallon tank).
 
Edited: By the way this tank is a bit more than one month old and it has been cycled for about 10 days.

 

[N0body Of The Goat]

Just like your Black Ghost Knife Fish going back to the store,  Platties are not suitable for a 10g long term, they need at least a 90x30cm footprint tank and usually groups of 8+ keep aggression in the group (albeit 8 would fully stock a 90x30x30cm ~81l tank).
 
Your ~38l tank is not suitable for most hobby fish, your responsible options are extremely limited. Two options that come to mind are either a Betta OR 4 Guppies.

 

[the_lock_man]

Check out the pinned thread in the Nano Tanks section, full of ideas for fish for tiny tanks.