1. Gate valve are not directional.
2. They can be a PIA as they are prone to getting stuck open or closed, and, particularly the cheaper ones, to having their spindles snap if turned too tightly.
3. Lever valves are, in my opinion, a better option, unless the finer flow control of a gate valve is needed.
4. If replacing gate valves with lever valves, the new valves:
4.1 Should be full bore.
4,2 Should be a decent make, as the cheap ones are prone to leaking.