Weave polls are very easy to make, it's the first thing we made. Jumps are easy as well, depending on how elaborate or simple you want them to be. I'm not sure how you would make a tunnel though, I just bought mine since it's Jake's favorite piece of equipment and sending him through makes for a great reward every now and then. We got it from Affordable Agility.
Something even better to make would be a ladder or a buja board. The ladder teaches (or reminds) the dog that he has back feet as well as front feet! That'll be important for agility (dog walk, teeter, jumps, etc.). The buja board (which can just be plywood with a partially deflated ball underneath) helps with balance and gets the dog used to things moving under their feet (like the teeter).
And just a reminder, since it looks like Merlin isn't a year old yet you'll want to go easy on training the weaves (the bouncing action can be hard on their joints) and no jumping higher than his hocks (even better would be just a couple inches off the ground. Jake is 18 months and we still only jump 16" once in a blue moon at class.
Good luck and have fun building!!
Only after the last tree has been cut down, only after the last river has been poisoned, only after the last fish has been caught, only then will you find that money cannot be eaten. - Cree prophecy