i am arriving with the easy jet flight from venice ,and I have booked
an hotel in marleybone.
I think that arriving in victoria station could be fine.

In that case your best bet is to take a South Central service from
Gatwick rail station to Victoria. Once at Victoria, follow the signs to
the London Underground and take a northbound Victoria Line train to
Oxford Circus. Get off at Oxford Circus and switch to a northbound
Bakerloo Line train to Marylebone. The exit from the Tube station is on
the National Rail concourse; turn right and you should see the exit.