When I first started playing the game, one of my goals was absolutely completing the catalog; however, when they added fortune cookies and event items that cost LT, I had to rethink what my goal was. Fortunately, the cookies and events are separated into the "special" catalog, and I know I will not complete that unless trading is added to the game. My goal for that now is to complete as much of the special catalog as possible without using LT & so far I've only missed three items that I could have obtained without LT: the wedding-party table, white wedding shoes, and white formal pants. My playtime was a bit low during that scavenger hunt, and I was a bit burned out on all of the events, but I have collected every other "free" item from every other event since the beginning. Now, when we have items that cost LT, I only buy the stuff I'm genuinely interested in. I ended up buying the LT mario event items, and I ended up regretting it because I don't particularly care for those items. 
Now, let's talk about the other catalogs! I still have a goal of completing the furniture and clothing catalogs, and I'm getting close! I have 332/338 of the clothes and 835/921 of the furniture. Below is the breakdown of what I still need...
MISSING CLOTHES 
- 3 floral shirts
- 2 friendship level tops (from the new villagers)
- Pharaoh's Outfit (from the fortune cookies) 
MISSING FURNITURE
-28 pictures (working on leveling all villagers to 20)
-19 special request items 
-19 floral furniture items (mostly tulip) 
-13 craftable items (from the new villagers/will be crafted in the next three days)
-4 floral bears (all tulip)
-2 OK motors furniture items
-Nook's Model Home (fortune cookie item)
Ideally I will complete the furniture and clothing catalogs soon, and then it will just be upkeep by crafting any new furniture and leveling any new villagers to get the shirts, photos, and unlock the special request items. I will have a bit of work to do on the floral furniture & garden events do tend to get in the way of that, but I'm nearly done with all the pansy items, so I will focus on tulip items from there. The thing I'm dreading most about finishing the furniture catalog is spam playing the OK Motor mini game, but I'm nearly maxed out on FP, so it needs to be done eventually. Anyhoo, if you're a competitionist like me, the best thing you can do is redefine what a complete catalog is for you. Maybe you just want to collect all of the regular furniture, or maybe you want to work toward those floral items. Even though I can't have a fully complete catalog because of the special category, I still find it satisfying to work toward completing the catalogs I can. Also, part of me is still hopeful that trading will be added down the road, and when/if that happens, I will very likely start working toward a fully completed catalog, and hopefully by then everything else will be done. Anyhoo, sorry for the long winded post & unnecessary breakdown. I'm just a nerd, and I actually enjoy going through my catalog to make my nerd lists of goals to work on.