As your filter bacteria are unlikely to be of sufficient numbers to deal with some of the chemical waste and bi-products of your fish yes, I would do a daily 10% water change for a few weeks (of water the same temperature), treated with tap water conditioner or dechlorinator etc.
With respect, I think 10% is not going to be nearly enough.
My personal recommendation would be to invest in decent quality liquid test kits for pH, ammonia, nitrite and nitrate. I personally started off with the Hagen master kit, others recommend the API, and others the Salifert tests. Certainly, the API one can be bought for £20 on Ebay. The paper tests can be somewhat inaccurate, so I'd suggest not getting those.
With the position you are in, you need to test your water at least once per day, perhaps twice, depending upon the results. Initially, you need to concentrate on ammonia and nitrite. These are both highly toxic to fish. When you test, if either of these two poisons is above 0.25ppm, then you need to change the water, by a quantity large enough to bring that level down as close to 0 as possible.
If you have a level of 0.5ppm for ammonia, if you only change 10%, then you will be left with ammonia at 0.45ppm - hence my initial comment. If, on the other hand, you change 75%, you will be left with 0.12ppm. This will give you some leeway to eat, breathe, sleep, etc., before you test again. You might well find that levels are up at 1ppm, or higher. It is perfectly acceptable to remove so much water that you only leave the fish just enough to swim upright in. They will find it much less stressful than swimming in a tank full of poison.
As time goes on, you will find that at one point, your test will register Double Zero (ie 0ppm ammonia and 0ppm nitrite). THis is good, you don't need to change water. But the next day, you will see levels rising again - in which case, change water again.
Then you'll find you can go 2 days without changing, then 3, 4, 5, etc.
When you find that you can go for a whole week without a water change, you can consider your filter as mature - at which point weekly water changes, of about 30%, are the way to go.
It is only at this point that it is wise to add further fish. However, you will then need to test daily, and potentially water change again, as the filter bacteria colonies grow to process the addition ammonia produced by the additional fish.
I hope that's all understandable, if you've got any queries, however daft you think they are, feel free to post them up, there are loads of us on here who are more than happy to share their experience, and give you all the advice you need. The only silly question is the one that remains unasked.
Edit: Sorry, the other thing to say is that you don't "need" a certain amount of fish per gallon.
As someone new to the hobby, many would recommend that you stock the tank lightly, but there are no set-in-stone rules - when you get a mature filter (in a few weeks), post up your ideas on additional fish, and see what people reckon.
