first look at your bufferpool size. The standard is 4 MB (1000 blocks) for each database. Depending on your needs and your memory size you should enlarge it to a reasonable size. Use control center to do this.
Later, it makes sense to separate data an indexes into different bufferpools. Read the manual, how to do this (you need new bufferpools, tablespaces related to the bufferpools and table definitions with an index clause).
Use design wizard for tuning all the other parameters, but have a careful look on the proposed changes!