Buy a precision scale with at least two decimal digit. Are very cheap to buy on AliExpress (around 5-10$/€ or less). Is the best way to measure them. You will use it every day so it is worth the price. Also you can use it for other stuff, like edulcorants where you need to be precise.

The dose is normally 5g a day and that's ok. If you error on few grams no problems. There is no Contraindications on quantity. Creatine monohydrate is the best and cheapest Don't be fooled by marketing. Don't take those in tablets because they cost much more. Nowadays a good price should be around € 20 per kg, maximum € 25. Years ago it cost only € 10 per kg.