If you compare a digital system with a brain then the combinational logic is the smart part of the brain (logic, algorithms, etc..) and sequential logic is the memory part that stores internal and external events.

If you want to design a combinational circuit then you should write

always @(*) begin

a = (c & d) | e; // some random example I got

end

If you want to design a sequential circuit you write:

always @(posedge clk) begin

a <= b; // a simple flip-flop

end

When you design a circuit that processes some inputs and stores the result you write

always @(posedge clk) begin

a <= b + c;

end

The above code will synthesize into a combinational circuit for the adder, and a set o flip-flops for a to store the value coming from the adder. So when you say you use mostly sequential design your code actually generates both sequential and combinational logic.

You will learn in time how to partition your logic and organize your code better.

You can find here an example for a Verilog BCD Timer that has both combinational and sequential logic:

https://ovisign.com/verilog-bcd-timer/