Fish!

With all goldfish there are several ways to try and identify their sex!

If your goldfish is a male it will develop breeding stars on his gill covers and along the first ray of his pectoral fins when he reaches sexual maturity, it will look something like this 

They will be white dots so care should be taken not to confuse them with ich or vice-versa

Another way to tell is when goldfish are ready to breed you will see a difference in their vent. The males will be longer and indented like this

while the females is not as long and will protrude like this

Less reliable methods would be to (after they reach sexual maturity) look at your goldfish from above as generally speaking females will be slightly more round than males

Also a breeding behavior of males is that they chase the females and bump in to their vent area, but again this is not always a reliable method

Here it and article on sexing goldfish: http://thegab.org/Goldfish/sexing-goldfish.html 

For the goldfish you should pick out tough plants or kinds it wont want to eat, I recommend Java Fern, it can be tied to drift wood or wedged between rocks and doesn’t need it’s roots buried, it’s also very hard to kill and can survive in low lighting. Java moss is good as well and so are Anubias and Echinodorus plants when it comes to goldfish and beginners. You can also put the plants in small terracotta pots and place them in the aquarium, you can buy a CO2 supplement to add to the water to help with growth and just make sure they’re getting enough light!

Here is a helpful website  http://www.aquaticcommunity.com/plants/settingup.php