Answer depends on your template abundance and how often you will need/want to make cDNA.

If you are working with middle to high abundance, 1:100 should be fine. This will give you a lot of cDNA to make PCR reactions for especially if you adhere to the triplicate technical replicate guideline.

Hello,

For preparation of cDNA i usually use 1~5 microgram RNA for 20 micro liter cDNA and dilute the cDNA 1:100 ratio.