1)is it better to have the filter inside the tank, or have an external one?
2) do i have to have an iluminator or will daylight be enouch?
3) where should i put the iluminator?
You'll probably get more answers in the correct section - in your case probably the Hardware section. This part is mostly for "hello's and introductions
But I can try and help you out a bit, but first a question for you ?
How big is your tank ?
External filters are great as they are much easier to maintain and offer much better filtration (on a like for like basis) than an internal. But externals are "mostly" used on tanks of 20 US gallons upwards.
2) do i have to have an iluminator or will daylight be enouch?
Again, do you mean the light ?
If so, then they usually just attach with some clips to the lid of the tank. But that of course means that your tank needs a lid. Does it ?