Leveling BR the Smart Way
First off, BR is not everything. It's a general guide so you can compare two things and see which is better. We've all seen the cashers who have the heros, gear, angels we can only dream of (or wait months to get). And we've probably beat some of the ones who did silly things or gotten beaten by people with 50k BR less then ourselves.
I'm going to start with the very basics and a fresh roll for our new members. The tricks will be later or in the class guides.
1) Upgrades (soulstones & blessed stones) - Your upgrades should always focus on your mount first to improve your mains abilities. You will do the most damage and survive longer then any hero. If not... level the damn mount! Each time you level the mount you gave a 5% stat increase across the board (and a nice jump in BR). Once the mount starts getting too expensive, slowly level a hero, preferably three levels at a time (lv 3, lv 6, lv9, lv 12 etc). Thats when they will get the biggest stat/ability increase.
2) Heros - Until level 50 or so heros don't really matter much. Level 3 gems in the heros are prefectly fine to start. Astral child is very squishy, she is however needed for the infinate rage build (unless you cash and get HoC Light Envoy). It's a serious pain in the neck to get her after 60 because you need the garnet herosouls. Even if you aren't sure if you will do the IR build, I highly suggest getting her. 75% of the time, this is the build where they have much, much lower BR and kick your ass.
Elements - This is a beautiful and straight forward way to raise BR and gives your heros a huge amount of survivability and damage. For the first few 1k BR you can get away with normal to save resources, but you'll quickly start rolling more red deductions then improvements, more up to advanced and ultra as needed. Low levels of elements on your heros are usually the main reason they die or are ineffective.
3) Gems - Your main should be at least two levels higher then your next best hero. As an example, if your main has mostly level 9 gems, then your next best hero should mostly be in 7s (a few eights are ok until you're ready to upgrade to 9-10 on the main). Your worst hero might only be in a mix of 5s or 6s.
Intially, you'll be starved for gold and gems and synth scrolls. I wouldn't recommend exchanging gems early in the game. I'll go into detail about gem priority in the class guides but to start HP, patk (hunters/warriors) or matk (mages), mdef & pdef will be your focus. As you can, start adding in dodge asap. Finally, open up gem sockets as fast as you can (without spending much).
4) Angels - You should be able to unlock angels fairly quickly. Nocturna is your basic lady. Level your first angel as fast as possible, it's ok to unlock nocturna to epic (purple) but I wouldn't recommend going further. As soon as you can switch to Marina (warriors/hunters) or Glacia (mages). You will then most likely switch to Boadica and then Aoede (or Nyssa or an event angel)
If you spend $5 you can get Lunaria. If you do, use her from the start and stay with her until Boadica.
5) Party formation - This intially will depend on Angel Halo. Usually your main is in the center back row. A warrior/tank type is in the center front row and dps is on either side.
Reasons to change party formation. 1) World Boss or guantlet 2) Totems 3) You need a specific strat to beat someone
6) Gear - Again focus on your main character and then one hero first. Always upgrade helms and weapons first, that gives you more health and more dps. Next your chest and legs, finally the ring and boots.
7) Character skills - unlock them as you can. Warsoul costs get insane so it's never a horrible idea to plant/steal some.
See the section on awakening skills for level 70 options.
8) Runes (gotten from Eternal Spire) - Primarily these will go on your main. At least until you've unlocked all 6 gear boosts to 100%. You can occasionally upgrade your heros, but you will get the most bang focusing only on your main.
9) Gem enchancement - Follow the same pattern as for gems. Your main gets the most, and you want to be at least 2 full bars above the next best hero. For example, you'll be level 9.1, your next hero will be maybe 6 or 7, the remaining heros will be lower.
Summing up everything quickly. Always focus on your main- gems, new gear, gear upgrades, gems, resources of any kind. That includes upgrading and training your mount. Next... upgrade in the right order and what's best for your class/heros. I.E. If the hero is a tank, there should be no attack or crit or hit on your gear at all. I swear to you, if you try to evenly level everything (and you aren't a serious casher) you will almost always be weaker then someone who is focused. It might be a 20k hit in BR to have some level 5 gems on the weakest hero, but the level 7-8 gems on your main are better in the long run.