Javascript (Babel Node), 145 bytes

   d=>{s=0;Array.from(d).map(c=>{s+=/[AV]/.test(c)?1:(/[NZ]/.test(c)?2:(/[MW]/.test(c)?3:(/[CU]/.test(c)?-1:(c=='S'?-2:(c=='O'?-3:0)))))});return s}

Try it online!

This is my first code golfing. I hope I'm doing it right.

I'll be glad to get some js golfing tips (before exploring new golfing languages) and overall golfing tips.

Javascript (Babel Node), 131 bytes

d=>(s=0,[...d].map(c=>{s+=/[AV]/.test(c)?1:(/[NZ]/.test(c)?2:(/[MW]/.test(c)?3:(/[CU]/.test(c)?-1:(c=='S'?-2:(c=='O'?-3:0)))))}),s)

Try it online!

This is my first code golfing. I hope I'm doing it right.

I'll be glad to get some js golfing tips (before exploring new golfing languages) and overall golfing tips.

Javascript (Babel Node), 179 bytes

process.stdin.on('data',d=>{s=0;Array.from(d+'').map(c=>{s+=/[AV]/.test(c)?1:(/[NZ]/.test(c)?2:(/[MW]/.test(c)?3:(/[CU]/.test(c)?-1:(c=='S'?-2:(c=='O'?-3:0)))))});console.log(s)})

Try it online!

This is my first code golfing. I hope I'm doing it right.

I'll be glad to get some js golfing tips (before exploring new golfing languages) and overall golfing tips.

Javascript (Babel Node), 145 bytes

   d=>{s=0;Array.from(d).map(c=>{s+=/[AV]/.test(c)?1:(/[NZ]/.test(c)?2:(/[MW]/.test(c)?3:(/[CU]/.test(c)?-1:(c=='S'?-2:(c=='O'?-3:0)))))});return s}

Try it online!

This is my first code golfing. I hope I'm doing it right.

I'll be glad to get some js golfing tips (before exploring new golfing languages) and overall golfing tips.

Javascript (Babel Node), 186 bytes

process.stdin.on('data',(d)=>{s=0;Array.from(d+'').forEach(c=>{s+=/[AV]/.test(c)?1:(/[NZ]/.test(c)?2:(/[MW]/.test(c)?3:(/[CU]/.test(c)?-1:(c=='S'?-2:(c=='O'?-3:0)))))});console.log(s)});

Try it online!

This is my first code golfing. I hope I'm doing it right.

I'll be glad to get some js golfing tips (before exploring new golfing languages) and overall golfing tips.

Javascript (Babel Node), 179 bytes

process.stdin.on('data',d=>{s=0;Array.from(d+'').map(c=>{s+=/[AV]/.test(c)?1:(/[NZ]/.test(c)?2:(/[MW]/.test(c)?3:(/[CU]/.test(c)?-1:(c=='S'?-2:(c=='O'?-3:0)))))});console.log(s)})

Try it online!

This is my first code golfing. I hope I'm doing it right.

I'll be glad to get some js golfing tips (before exploring new golfing languages) and overall golfing tips.