Hey, welcome back to the game, and welcome to Reboot.
Monster codex is one thing you need, monsters drop two types of cards as you know, if you get all the monster cards in one place, you can get a stat boost bonus. People tend to collect all the monster cards from monsters in Leafre because its set bonus increases attack, but you currently can't complete this set because Dragon Rider party quest is glitched still apparently. These are cards you just pick up, not the ones you use for familiars.
Also, I'm pretty familiar with Angelic Buster, however not an expert. But, I will share what I know, Trinity is your bossing attack (until you reach level 170 and unlock the Supreme Supernova hyper skill), you have to tap it to make the most out of using it. Having Soul Seeker active is good for when you wanna train or do some extra damage to bosses, it'll send out projectiles and hit monsters nearby. If you wanna charge your attack so you can keep using skills that require charge faster, you should use Star Bubble since it has the highest recharge chance when used and its animation is quick too.
If you don't have very good armor at the moment, Zakum (make sure it's Normal Zakum) drops a pretty decent weapon (level 110) until you can get the Pensalir set. Pensalir equipment drops from level 140+ monsters, you'll make your way there eventually, some train from 130 to 150/160 in a theme dungeon called Korean Folk Town. What you want are Moon Bunnies, until like level 140, then go to Yellow King Goblins until 150. Unless you participate in parties or can mob well enough, then Moon Bunnies are good enough and you won't have to move on to Yellow King Goblins. Just remember to open the world map, click on a location, and enable the auto-navigation feature.
Hilla and Magnus are two more bosses you can take on for equipment for your level, Hilla drops Necro equipment, which is for level 120, and good for the set bonus until you move on to Pensalir. And Magnus drops a badge, shoulder, cape, and boots for level 115+.
One thing you might not be aware about, are Link Skills and Character Cards, you basically make other classes, and level them to 70/120-140/210, you'll want to make a lot of characters because these will boost your main character, and the other ones you play all around. The second level for link skills is going to be changed to level 140, so make sure to keep that in mind. The characters you want to level to at least 70 or 120-140 are;
Mercedes (for EXP boost)
Aran (for bonus combo EXP)
Evan (for extended rune duration, it'll increase the time for the buff that earns you bonus EXP)
Demon Avenger (for damage)
Demon Slayer (for boss damage)
Kanna (for damage)
Beast Tamer (for boss damage, critical rate, and HP/MP increase)
Phantom (for critical rate)
Luminous (for IED/PDR)
Hayato (this link only has one level, it increases all stats by 10, and attack/magic attack by 5%).
And optionally;
Kinesis (for critical rate)
Cannoneer (for 15/25 to each stat, and 5/10% to HP and MP)
Kaiser (for HP)
Cygnus Knights (for elemental and status resistance, to get the most of it, you'd need to level all its classes).
Aran, Evan, and Mercedes are the top 3 to start with, so you can start there especially if you want an easier time leveling, just don't forget to go into the basic skills tab and open the link manager, and activate the links you want. You may change links once a day, and only one character can use a link skill at a time. So don't forget to change it if you want it on another character.
Now that Link Skills are out of the way, I'll tell you a bit about Character Cards. There currently are set effect bonuses, but those will soon be removed. To get these bonuses, you have to activate 3 cards of the same class (I.E. Warrior, Pirate, Mage) to get these bonuses. If your main is Angelic Buster, these are the sets you'll want, but keep in mind these set bonuses will get removed, so whether you want to still work to get them is entirely your choice.
Pinpoint Aim (3 Bowman Cards – Final Attack damage) +1/2/3/4%
Weak Point Targeting (3 Thief Cards – Critical damage) +1/2/3/4%
Pirate’s Way (3 Pirate Cards – Ignore Enemy Defense) +2/4/6/8%
The card grades are as follows; grade B - level 30, grade A - level 60, grade S - level 100, grade SS - level 200. You want S cards at least. And the cards you'd want to obtain are;
(It's your choice which to start to get first. A small note, Beast Tamer isn't available at the moment, but in the future it may get released again.)
Aran: +70% chance to replenish HP on attack every 60 sec. Replenish HP 2X when attacking multiple monsters. Replenish HP +2/4/6/8%
Battle Mage: Damage when hit -2/3/4/5%
Beast Tamer: Ignore Enemy Defense +2/4/6/8%
Blaster: Ignore Enemy Defense +1/2/3/5%
Bow Master: DEX +10/20/40/80
Dawn Warrior: Defense +2/3/4/5%
Demon Avenger: Boss Damage +1/2/3/5%
Shade: Critical Damage +1/2/3/4%
Hayato: Critical Damage +1/2/3/4%
Kanna: Boss Damage +1/2/3/4%
Marksman: Critical chance +1/2/3/4%
Mechanic: Buff duration +5/10/15/20%
Mercedes: Skill cooldown -2/3/4/5% (Takes priority over item potential. Cooldown cannot be lower than 1 sec)
Mihile: Defense +2/3/4/5%
Paladin: Final Physical Damage +(0.5/1/1.5/2 * Playing character level)
Shadower: Speed +2/3/4/5%
Thunder Breaker: Final Damage +(2/3/4/5 * Playing character level)
Wild Hunter: 20% chance to deal 4/8/12/16% increased damage when attacking
Wind Archer: DEX +10/20/40/80
Xenon: Bonus Stat +5/10/20/40 for STR, DEX, and LUK.
Traits are also something that'll help you, you may have noticed you get willpower, charm, diligence, insight, empathy, and ambition. These level up over time, and give you stat boosts.
Amibition - IED, reduces EXP loss on death (you can easily get a lot of ambition from doing bosses, mini-bosses. The Silent Crusade questline is really good for this.)
Charm - Unlocks the pocket slot, unlocks quests for free expressions (you can get charm from equipping equipments, and cash items, also from fame others can give.)
Willpower - HP, Defense, Abnormal Status Resistance (you can easily get more willpower from staying online, or by completing party quests.)
Diligence - Double mastery rate, scroll success rate (this one doesn't really matter much in Reboot, other than the mastery rate which is for professions, and the scroll success rate doesn't benefit potential scrolls.)
Insight - Ignore Enemy Element Resistance, and increases the level in which you get free item potential reveals (you can gain more insight by mining ores.)
Empathy - MP increase, Buff duration (to level this, you'll want to get the herbalism profession and pick herbs.)
