There are so many threads on this subject already :/ Go read some stickies on the "General Discussion" section.. There is a thread on cycling, stocking, maintenance and feeding.

You can't have koi in a tank, they grow far too big for that.
External filter with 550gph minimum and rather pick a maximum of 4 commons/shubunkins/comets.
Add the plants before the cycle and if you have any, use old tank water to help it cycle or start off with one goldfish in the tank and introduce the others after a month each to make sure the ammonia doesn't get out of hand.

Dragonii , i live in the U.S.  Tennessee to be mor specific lol n i am thinkn bout getn that Aquatop Filter that u have told others about. 

Dragonii: Lol thats exactly what I'm looking cheap but powerful..
Nossie: should I use plants that are already established or could I use the new bulbs..I'm not sure if I said that in a way where it's understandable to other ppl besides me lol sry in advance if you have no idea what I'm trying to say lol
 Just so excited I can't wait lol 

yeah that answers my question lol  sorry I was in a hurry when I posted that 

I have thought bout getting the fancy goldfish.. but I really want common goldfish I don't know why but I like them more than the fancy.. My ultimate plan is when my fiancé and I get married and move in to our new house together we going to build a pond for the goldfish and maybe some koi depending on how much space we have then I thought that we could get some fancy goldfish to put in the 55  lol but that's awhile away tho lol 

Hmmm I'd say maybe stick to 2 or 3 goldfish.

If you aren't sure how long it will be until you get a pond, you would want the fish to have as much space as possible until then

I know the rule of thumb is 40 litres per goldfish, but I really wouldn't apply this to single tailed, purely because they grow more and require more swimming room than fancy goldfish (as they are quite speedy, Lucky often does 'laps' of the tanks XD). I would double it and say 80 litres per fish at a minimum, but if you can give it more space, then absolutley do.

Dots, I currently have a common goldfish on her own, she has been moved from a 21 litre tank to a 90-100 litre tank, that is 3 foot long and she is going to grow out of this. She is only a baby at 3 inches, but when she reaches around half her potential size -so 5/6 inches- I am either going to upgrade her tank to something huge like a 6 foot tank or build a pond, or if those options fail, find someone who has a pond.
Given that she's probably stunted from being in a small tank for too long, I am not sure how long it will take her to grow, hence why I'm going by her size as an indicator of when to upgrade not by any time length.

So you can keep 2 or 3 single tailed fish in a 55 gallon/250 litre tank as a temporary home, but they will need to be upgraded. Goldfish grow pretty fast, so please keep this in mind. You may need to upgrade their tank, depending on how far away in the future the pond is.

All the best with the fish Dots, I would love to hear how things go  

The fish prefer natural colors in their tanks Which is pretty obvious, I also think the patterns of the goldfish show much better against a more neutral colored gravel.

I use Aquatan by Sera or Stress coat by API as water conditioner and Easy Life Fluid bio filter medium for beneficial bacteria (it has both in one) and Stress zyme by API together with stress coat whenever I have those on hand.
Easy balance could be used, but I'm not entirely sure if it's necessary as long as you keep sensible stocking levels in your tank and keep up the regular water changes (50% every single week)

I use Stress Coat as my water conditioner and Stress Zyme as my beneficial bacteria

If the pond is less than 2 years away, you should be okay, but do keep an eye on the goldfish growth, it's difficult to judge sometimes when is best to move them.
For example my Lucky grew an inch or two, in the first few months I had her, then she just stopped growing and has probably had her growth stunted from being in a tiny tank for so long,  but this was a common goldfish in a 5 gallon tank! You will notice when their growth slows or stops. I imagine it won't be as quickly either, so you should be okay, just keep an eye on them  

If you haven't brought the tank yet, you could always go for a slightly larger tank now, like a 65 or 70 gallon, it depends on your space and budget really. Oh also try and find a nice long tank, longer tanks allow more swimming space.
So even though my tank is only around 29 gallons -it will need to be upgraded later- even though it's quite small, it is 3 foot in length, so Lucky has tons of space to swim along in, given her current size is 3 inches

Good luck, be sure to shop around, take your time and have fun

nothing wrong with aquasafe

Thanks y'all I was wondering if I do a fish less cycle would I have to use the tap water conditioner or not?? I think of some random questions, I know lol.

Thanks skwishee for the good wishes

I would also use the conditioner And lots of beneficial bacteria! But you wouldn't have to change out the water that often while there are no fish in the tank