If I cast Truesight on myself, and then I perceive thru my familiar, will I get the benefit of Truesight? If not, if I cast Truesight on my familiar and then observe thru the familiar, would I get the benefit?
...Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has. During this time, you are deaf and blind with regard to your own senses.
If I cast Truesight on myself, and then I perceive thru my familiar, will I get the benefit of Truesight? If not, if I cast Truesight on my familiar and then observe thru the familiar, would I get the benefit?
The second option makes the most sense to me. You are limited to the perception of your familiar so, it makes more sense to enhance it's senses.
You will want to go with option 2.
"Not all those who wander are lost"
One of the two has got to work. Ask your DM which if you're in any doubt. Agree casting on the familiar seems more logical.
Option 2. You use the familiar's senses.