From Gatwick Airport, which is about 25 miles south of central London, you need to get into cental London first, then you can the tube out to Tottenham, which is in the north-east of London.

The quickest and easiest way from the airport into London is by train. There is a station right at the airport, with many trains running at all times. Allowing about an hour to clear customs and immigration and get your luggage, you should have no trouble getting a train at around 6am on a Saturday morning. Travelling with luggage at that time should not be too much of a hassle, it wont be too busy yet.

Some trains stop at ALL the local stations on their way to London, some stop at only a couple of stations, and some are non-stop expresses straght into London (the Gatwick Express mentioned above is the fastest non-stop train but also the most expensive option..it currently costs about £22) .

All trains from Gatwick, regardless of how fast they are, arrive at Victoria station in central London.

At Victoria, go down into the Tube and get a northbound Victoria line train… it depends where in Tottenham your cousin lives, there are various stations in the area and you’ll have to check with her which is the nearest to her house. But the stations at Tottenham Hale, Seven Sisters, and Blackhorse Road are all in the local Tottenham area.

If you want to do it really cheaply, then buses will certainly be running, but the road journey from Gatwick into London is a long and slow one. Once you get into cental London, there will be plenty of buses towards Tottenham but its not a good idea to travel with a lot of luggage as they can get pretty crowded.

I would take the First Capital Connect train to Kings Cross. From there it depends exactly where your cousin lives. You can take the Piccadilly Line to Turnpike Lane or Wood Green for west Tottenham or the Victoria Line for the rest. It is also an easier interchange than Victoria..