Small budget: 18- 135 or 17-50+50 1.8.

In the budget: 15-85 or 24- 105+35F2 or 50 1.4.

Big budget: 24-70+70-200+35 F2+50 1.4.

That's basically it. The above is the general direction of zoom and fixed focus used in portrait photography on C frame machine. Choose to buy according to your own budget. For reference.

Answer supplement:

If the budget is less than 4,000 yuan, you can buy double fixed focus, provided that you have any zoom head, two fixed focus 35 F2+50 1.8, the total price is about 3,500 yuan. If there is no zoom head, change it to a certain value: 18- 135 disassembled version +50 1.8, and the total price is about 3,000.