Gabriel,
What you have in mind is not practicle for several reasons.
$200 wouldn't even buy the materials for such a boat.
Building a fibergalss boat over a male mold is technically demanding. The hull has to be close to perfect on the mold because corrective measures like sanding and filling are not practical.
It is also physically demanding. The hull laminations are usually done wet on wet. That is, you start laminating in the morning and continue until it's done even if it takes 24 hours. It is best done using at least three people who know the ropes.
Finally, I lied. I haven't built a fiberlass boat. I considered it but after reading the previously mentioned book I decided it was too demanding.
I have built a canoe that is close to your ballpark figure of $200.
I built a boat called "Cheap Canoe" for $265. It's a stitch and glue pirogue (flat bottomed canoe). The plans are a free download from bateau2.com. Check it out. Their web site is down at present but should be up and running shortly.
Charlie

: I want to make a fiberglass canoe, but don't have $ for a plug/mold. I was
: wondering if I could tape some layers of wax paper to the bottom of a
: canoe and lay up 2 layers of 6oz. cloth to copy its shape. Then, remove
: and reinforce the inside with more glass etc.??

: Anyone have a way to build a canoe for under 200$ w/ minimal effort?

: Thanks for any advise.