More easy guides here to get 100% here

1) Start the game select adventure (circled image 1 below) simply play 25 levels (1 level has 3 rounds by 3 different characters). The following achievements will unlock as you progress image 4 below. I suggest using auto battle where the computer chooses your best cards and plays them for you. You get to settings by choosing the cog bottom left of your screen (blue square with a cog in it) Image 3 below shows the settings I have chosen.

These achievements are all earned by researching combos. Simply go the research (circled in image 1 below) and choose 2 different cards to put in the machine when they're done it counts as 1. You have 2 free chambers so use both (image 2 below). The achievements you get for doing this are image 3 below.

This is not hard and you just keep going till you get to level 15 in the arena. Remember to have auto battle on and keep upgrading your cards when you can. You upgrade cards at the Deck circled image 1 below also turn on auto deck there. When you upgrade 2 cards the same you can then combine them and upgrade again. The higher the number the better the card (image 2 below). The achievements you get for doing this is image 3 below. You will also get achievements for upgrading cards image 4 below.

For the achievement The Quest for More Power use common cards as they cost less to upgrade. Level them both up to level three - if they're rare level them up to level four. Fuse them together. Level up and fuse the two level one cards. You should get the option to fuse the upgraded cards, click fuse and the achievement will pop.

Top left of the screen is your character simply click on your character and choose a different one (that you have unlocked).

Simply go to the bottom left of your screen (image 1 below) click the US flag. Choose a guild, join it and the achievement will pop.

You can purchase packs from the shop to get new cards using coins earned for pvp matches and daily quests etc. You also get free diamonds for completing quests.