Not ready for the New Wold, not ready for anything that they were going to have to face after the archipelago.
Luffy experienced what it would be like to lose his entire crew, to be left alone. The entire crew realized that they were too weak to be hold out on their own in the pirate world after this.
There were major threats, stronger pirates, marines, and they needed to be stronger not just to survive but if Luffy wanted to be the Pirate King someday.
Each of the Straw Hats experienced a crushing defeat, losing their nakama and being just one of the numerous pirate crews that get decimated in the New World.
They all resolved to be stronger, to be better at their job in the crew and become capable of supporting Luffy on his journey to be the Pirate King.
The timeskip began after Luffy’s desperate attempt to save Ace from his execution which ended in quite the tragic failure for him.
Luffy began his training with Rayleigh after announcing his plan to meet after 2 years, instead 3 days.
All the crewmembers understood this clue and were able to stay on the island that they were in, thanks to special efforts from Bartholomew Kuma.
Each Straw Hat made a vow to enhance their skills and become stronger to be able to support their captain, to the fullest.
1. Straw Hat Luffy
Luffy returned to the Maiden Island owing his life to none other than the Surgeon of Death, Trafalgar Law. After healing properly, Luffy started his training with Vice Captain of the former Vice Captain of the Roger Pirates.
Silvers Rayleigh. They trained on the Ruskaina Island that experienced all seasons very heavily only for the duration of 1 week each. The island was filled with hideous monsters and only the strong survived.
Luffy trained here learning to use all kinds of Haki: Observation, Armament and Conqueror’s. His tolerance to all the different seasons, his abilitiy to hunt and fend for himself increased dramatically over the course of these two years.
2. Pirate Hunter Zoro
Zoro begged Mihawk to train him in the way of the sword so that he would be able to protect his crew.
Mihawk agreed to train him with the help of the Humandrill monkeys that inhabited the forest, who had learnt various fighting techniques from the hideous war that had taken place there.
Mihawk taught Zoro about the Coating of Armament and had forbid saké for him until he hadn’t mastered it.
3. God Usopp
Usopp was sent flying to Byon Island. The entire island is a seeming wonderland made up of delicious junk food until the identity of the island is revealed.
The island is a carnivorous plant makes all the prey gain weight with all the delicious food so that they fall straight into its mouth as the flower closes up.
Usopp, despite falling or this trap in the beginning, manages to stay alive and is trained in the ways of a very new weapon, the ‘Pop Green’.
Pop Green are essentially seeds of carnivorous plants that grow instantly upon impact. Thanks to his teacher, Heracles’n, Usopp was able to learn and use the abilities of these plants to the fullest.
4. Black Leg Sanji
Sanji was sent to the island of daydreams the “Momoiro Island”, “Momo” meaning pink and “iro” meaning colour.
True to its name, the island is covered in peaches, pink flowers, and cherry blossom like pink flowers that drift through the wind.
Sanji is rescued by someone called Elizabeth. Sanji wants to thank this beautiful lady until he finds out that the island is home to the okamas and is ruled by none other than revolutionary extraordinaire, Emporio Ivankov.
Ivankov challenges Sanji that he would teach him the recipes only if he was able to get them from the Okama masters of the islands, but in return they would chase him day and night, not even letting him sleep, to try and put a dress on him.
Thanks to all the terror and constant running and fighting, Sanji is able to fly, have incredible observation haki and have his speed improved drastically.
[The anime also features a small part where Sanji awakens his ‘heart of maiden’and becomes an okama until the newspaper shocks him back to himself.]
5. Cat Burglar Nami
Nami is sent to a sky island, Weatheria which specialize in researching and manipulating weather.
Nami was able to trick the old folk in thinking she was going to jump off the island but as soon as she read the newspaper, she stayed with Haredas and pleaded him to teach her about weather.
She spent the entirety of her two years under the guidance of Haredas, manipulating and studying various different weather phenomena of the Grand Line while also improving her Clima Tact.
6. Cotton Candy Loving Chopper
Chopper flew to the Bird Kingdom where birds and humans were at war.
Chopper saved the life of a young chick and resolved the conflict between the humans and birds as well.
The village of the humans in the Bird Kingdom featured a gigantic library with advanced knowledge of both weapons and medicines.
Chopper was able to study, test and was able to transform into any of his transformations freely.
He could also control Monster Point for 3 minutes.
He was able to discover new points as well as boosted his existing transformations.
7. Devil Child Nico Robin
Robin was sent to Tequila Wolf where she was immediately captured while protecting and covering for an innocent slave girl.
Robin was rescued by the revolutionaries who she spent the rest of her two years with.
Robin trained and improved the usage of her devil fruit.
She is said to have gained an incredible amount of knowledge about the world and the ponegliffs during her time with the revolutionaries.
She made powerful allies in Sabo, Koala, Hack and so on.
8. Cyborg Franky
Franky changed the most during the time skip since he quite literally swapped out parts of his body, upgraded them using Vegapunk’s futuristic island, Baldimore.
Franky not only installed useful features like lights, guns and laser beams but also made weapons for the Sunny.
Franky made the ‘Black Rhino’ which is a bike and ‘Brachio Tank’ which is a tank and is able to now transform and dock into General Franky or Franky Shogun who also possesses a might sword called the ‘Plunderer’s Sword’.
9. Soul King Brook
Brook by far lived the most dazzling life during the time skip among the Straw Hats.
Brook became a music star who was known throughout the Grand Line as it touched the souls of the people who listen to his music,
This allows him to have them enjoy his show, make them fall asleep, create party or vanishing illusions and manipulate souls to some extent with his music.
In addition to this, Brook also can now get his soul out of his body allowing him to carry out recon missions in dangerous areas without risking anything, delivering messages phasing through stuff rendering him pretty much unstoppable through any kind of security.
The reason I haven’t included Jinbei in the list is because he wasn’t a part of the Straw Hat Crew at the time when the time skip happened.
The Straw Hats have worked hard throughout these two years and their efforts have only done them good.
The Straw Hats have been on a winning streak since their time apart, and we will only see them perform better and better in the coming years.