So! There are two Sindarin words for hope: "amdir" is the word for hope based on logic or observation (eg "it's really warm this morning, I hope that means it won't rain"), but you're quite right to use "estel", which is hope based more on faith (not specifically in a divine power, though!). It was also adopted into Quenya, which is handy - means you don't have to worry about translations.
How it looks is a slightly complicated question. The Tengwar are an alphabet, and like the Latin or Cyrillic alphabets, the letters can be used in different ways. In Tengwar this manifests as different ways of showing vowels, and there's three possibilities: like a Sindarin speaker, like a Quenya speaker, or like a Westron speaker, eg a Hobbit.
There are also multiple fonts available. I'm using Tecendil, which does a good job (avoid the English mode, because it mucks up the S). Some options for the text:
Honestly, I think the top left version looks best, but you can pick your own. :) The bottom row is roughly how I'd hand-write it. The middle row suffers because the Sindarin version looks like it's supposed to say "9pt" - nine points for what??