In the beginning it's tough alone but if you can get a party and attempt genocide on the early boss monsters (Ludo and the velociraptor) you can make their weapons and armor making future bosses "easier". Keep doing that on the mid monsters and the end monsters will be a breeze.
Honestly it's all about memorizing attack patterns. Once you have that down it doesn't matter what your armor is. Weapons still count if you want to kill before time expires.
I beat the entire game with my first earned armor set (yellow hoodie from Ludo) just because I liked the look. It was a pain with monsters that had fire attacks (almost all of them) or were in the desert but that's where the trial and error comes into play.
Afterwards I grinded for Agna's sharpness set and the game was easy mode. --- Games: WO3, Ragnarok, BLOPS2, PS Allstars, BM:AC, NG:RE PS3/Vita/WiiU: ENDBOSS78 3DS: 1375-7216-3398
I found watching videos before the release of Tri to be a big help with the initial learning curve. I was new to the series but managed to destroy the first two or three monsters without too much trouble because I already knew how to time basic attacks and manage item usage (probably one of the hardest things for beginners).
I also learned that you actually have to be good by the time you get to end-game monsters like Alatreon. I can't tell you how many people I teamed up with would just spam "wall, wall, wall, wall, wall." in the text box while Ala was in rage mode. Baffled me how they got that far in the game.