Mostly we use AMBA bus protocols AXI/AHB for the on-chip bus [backplane] communication in any SoC. So, learning AMBA protocols will be a huge advantage. You may want to learn APB too, as we use it for register configuration. So, AHB+APB is a very good combination, to begin with.
Also, learning the interface protocols like SPI, I2S, UART or memory interface protocols like DDR/LPDDR will give you an edge over others. Protocol knowledge alone might not help, you need to work on the IPs/VIPs that use those protocols and understand the implementation process. In the case of IP, RTL/VIP/TB coding, “How do you implement the protocol communication?” is important and the same gets scrutinized in the technical interviews. So, you really need to gain the experience of working on real-time projects.
We offer the opportunity to gain such work experience through our internship program which is a part of our all kinds of our offline courses at Maven Silicon ASIC Verification Course | SystemVerilog Training | UVM Training Courses | Verification Methodologies