"we have only 45-50 users on the premises so can I config VLAN ??"
Can you? Probably, on a L3 switch. Usually can also do that on many L2 switches that have management capability.
"Are these beneficial or not?"
That's a "it depends" answer. As Seb notes, the most common reason for using multiple VLANs for so few hosts would be to add security filters between VLANs.
"per VLAN how many hosts should be there or minimum no of hosts should be in VLAN you recommend ??"
Minimum? No minimum. Although if number of hosts in the VLAN will stay small you normally want to insure you use a smaller address block so as to not waste address space. However, on the small end, you might use an address block double or triple what you need for "just in case" assuming the larger address block still isn't "too" wasteful. For example, one or two hosts can be supported by a /30, but you might want to allocate a /29 or /28, again, "just in case", as neither of those is very large. Much also depends on what kind of address space you're using, i.e. how much "empty" address space you have to allocate from.
Maximum is another "it depends" answer. Traditionally using a /24 is usually "safe". Occasionally you need to go smaller. Sometimes, again as Seb notes, a /23 or even /22 or okay too. (BTW, on wireless you can often go even larger.)
