my pc is pentium 4 3.0ghz
1gb ram ddr2
geforce 9600 gso
I would suggest getting an Intel i5
A Graphics card from at least the 700 series
and getting 8 gb ram.
All of these items are budget and you can expect a good experience in other games as well. As for Raft, the game is not optimized very well, so it will still lag a bit compared to most games out there.