D-LINK Swhich & Fiber Media Converter

Your IT department understands your specific situation better than anyone here can. I suggest you trust their recommendation.

I can't tell you wether there's going to be problems or not, but one thing is for sure:

If you opt for a 6/8 port switch to add a few more PCs, you'll be about taking up all available ports, which will leave you in the same situation when you need to add a few more PCs in the future.

Regards

Unless you are concerned with physical security within your facility, there is no additional risk by placing the 6/8 as an adjunct.

It does hamstring you for future growth, as pointed out previously.

Why the need to purchase the fiber connection? Is that necessary? Is the D-Link layer-2 (the switch is)?

Why are you suggesting to the IT department what they "should" purchase? You should explain to the IT's what your needs are, they should make it happen after vetting all options. That's their job (support).

Dear Sir,

I have already request to our IT person. he suggested CISCO 24port switch which is available in 1500 to 1700USD & I need just 3 port which can be arrange through fiber media converter & small switch instead of above mention high budget job.

Kindly note that, purchase material cost should be charge to our department that is the reason of my problem.