The FQPF27P06 MOSFET is off (high resistance from source to drain) when the gate voltage is >=0V (i.e. positive) relative to the source. The MOSFET is on (low resistance source to drain) when the gate voltage is sufficiently negative relative to the source. The MOSFET resistance from source to drain decreases when the source-gate voltage is more than 4V (i.e. source is positive relative to gate) (also see FQPF27P06 datasheet, gate threshold voltage). As the source-gate voltage increases beyond 4V (up to the specified max = 25V; do not exceed!) the source-drain resistance decreases, becoming the minimum possible at 25V. However, little is gained by driving the gate more than 10V negative relative to the source; i.e. no need to apply full 25V. You must arrange your circuit to provide the indicated voltages for off and on operation of the MOSFET. Since V1 can be as great as 30V, it is unlikely that your function generator can directly provide the required voltages: relative to V1-, MOSFET off when gate = +30V to +55V (30V+25V) and MOSFET on when gate = +20V (30V-10V) to +5V (30V-25V). Thus, additional circuitry is likely needed to achieve the required gate voltages.
Designing and then building a switching DC-DC buck regulator is not a trivial effort! I have decades of design & fabrication experience, yet I would still purchase an off-the-shelf I.C. for such a design and I strongly suggest that you follow my advice. Ultimately your cost would be less and success more likely. Most manufacturers of DC-DC regulator I.C.'s provide example circuits either in the datasheet or in application notes. Your first attempt should be to follow such a design. Also, please search StackExchange for many other discussions relevant to your effort. An approach far more likely to lead to success would be to buy a complete DC-DC converter module that meets your requirements.
If you wish to continue your present course as a learning experience, then you have much to learn. Before you achieve an acceptable design you will almost certainly destroy some components, raising your costs and you will waste much time that you could have better spent on other aspects of your design.
In my opinion, the MIC5021 is not a wise choice for your current circuit for many reasons that I will not attempt to describe here.
Good luck. I hope that you decide to direct your efforts toward a less difficult goal.