Hi Wizzy! Welcome to Rescreatu - we're happy to have you! :)
Res is definitely the place for you if you're into collecting. We have Showrooms (under the Shops tab at the top of the page) where users can store Creatu that they've collected - it's basically a gallery for Creatu! We also have the Item Gallery, located under the Shops tab as well. This is a great place to show off your cool, rare, and themed items - something I've been meaning to do myself for a while!
You can feed your Creatu by obtaining a food item, opening your Inventory (the treasure chest icon near the top-left of the page), clicking the item, and clicking "Use Item". This will feed your selected Creatu. You can change which Creatu is selected by using the left and right arrows by your selected Creatu on the sidebar and clicking the "Select" button next to the Creatu you'd like to feed.
A more preferred method of feeding Creatu is the Food Pen (the apple icon, to the left of the Inventory icon). Food placed in the Food Pen will automatically feed your Creatu once their hunger levels get low. As long as you have food in your Food Pen, you don't have to worry about manually feeding your Creatu! :) You can add food by navigating to that page and clicking the "Add Food" button near the top of the page. Then, simply click the Food Pen bubble next to the item you want to store, and click "Complete Selected Actions".
You can obtain food in a variety of ways. You can pick free apples via the Apple Tree (located under the Games tab>Luck). Most users get the majority of their food in bulk from the NPC shops or by searching for the names of food items in the Merchant Shops.
Regarding making TU, this is entirely dependent on how you'd like to use the site and what your favorite activities are. You can earn TU by playing games, hatching rare Creatu and selling them to other users (via the Rancher Shop if you're a Rancher), stocking items in your Merchant Shop if you're a Merchant, or offering commissions if you have some type of talent such as coding or making art. I personally like to play the Stock Market (Games>Skill>Stock Market). The trick is to buy low and sell high, as with any stock market. :)
I hope this answered your questions! Please let us know if you have any more, or if you'd like me to clarify anything. For now, if you have not already, I recommend reading over the rules. They are located here: http://www.rescreatu.com/rules.php
It's a great starting point for new users and may help to answer some of the questions you might have.
Anyway, I'm sure I'll see you around. Have fun!