The stronger network adapter is not the answer most of the time.
You don't list your router, but start with a good 802.11ac router in a central location. Run network cable (CAT 5e) through the attic or basement where possible for a wired connection. If this is not possible, than consider a wired connection via a Powerline adapter. If the you still need a better wifi signal, than you will need an Access Point for a secondary wifi signal.
Avoid repeaters- they will halve your bandwidth as they must both transmit and receive.