Mandarins are definitely not a veteran rookie fish. They are very hard to take care of, even in larger, more established aquariums. It is possible to keep one in such a small tank if your sump contains a huge refugium and/or algae scrubber.
If you really want to do it right, look into drilling your aquarium. There's a glass holes kit that you can buy for like $45 and it comes with the overflow, bulkhead, glass bit, template etc. . If you are going to do some high intensive light coral, you're going to need an awesome filtration system or plan on doing some scheduled water changes.
Here's a pic of a 10g tank that a college student over on RC has. His handle is RockRyno. He won nTOTM this month I think.
Here is his equipment and stock list.
Equipment:
Tank: standard 10 gal
Filter: AC70 modded with a Nano-Glo LED fuge light w/ custom overflow
Heater: Rena 100w Smartheater
Light: DIY 36w LED array. Using 3w Cree LEDs (8 blue, 4 neutral white) both colors dimmable.
Livestock:
Fish - red Mandarin
Inverts:
the usual snails (no crabs)
red Bali starfish
sea apple
Crocea clam
Corals:
From Left to right: duncans
frogspawn
mohawk zoas
orange yuma
meteor sower hyphastrea
purple deaths
blue ricordea
rainbow acans
idaho grape monti
orange monti
fuzzy green mushroom
bubble coral
forest fire branching monti
blue tipped millipora
eagle eye zoas
ponape birdsnest
green birdsnest
bonsai acro
GSP
GB packer zoas
flower petal monti
fire and ice zoas
neon green candy cane
bird of paradise birdsnest
orange ricordea