What country are you from?
Okay firstly don't do full water changes, you'll shock your fish waaaay too much, do 50%-75% being careful to make sure the new water is the same temperature as the old, don't take the fish out when you do this.
Secondly the gravel syphon, okay stick the long thin end in a bucket, take the bit ground tube end and place in tank, fill with water and lift so the water drains to the bucket. Before the water finishes draining stick the big tube back into the tank making sure theres no air, and the suction will begin. Stick it in your gravel stirring the gravel up and collecting the gunk in there. Remove the big end from the tank when you finish vaccuming.
Thirdly, since you don't ahve test kits, I assume you haven't cycled? do you have a filter? You need to get test kits ASAP and do 5-% water changes everyday. Goldfish are messy creatures, and if the tanks not cycled they won't be happy. Look up cycling on the forum, theres heaps of posts.
Now how big is your tank? What sort of goldfish do you have? Thin ones with a single tail (comets, shubunkins, commons, feeders) or more egg shaped ones with a double tail (fantails, all fancy varieties). Single tails need at the very very very least about 50g/200l each, and are better off in a pond, they can get to two feet. Fancy varieties need at the very very very least 20g/75l for the first, 10g/40l for every additional goldie after that.
It is ill advised to add a cleaner fish, goldfish do best in a species only tank, no other fish. Any cleaning needs to be done by you.