I would recommend making a portfolio and placing it in a webpage, since you will only be using it for showing people your previous work, even a wordpress or blogspost might work just fine, even though it might look a little unprofessional.
If you have a few bucks to spend, you can get a .88 cent domain and a cheap hosting and just install a wordpress theme specifically for portfolios, making a better impression on the client.
Once you have all of the above, start advertising yourself through social media, like Altech said above. Best of luck!