Okay, I read a few posts here and I'm going to have to take issue with a few of them. Not because I think those people are wrong... But, because I don't think they're addressing your real question and you're not quite clear on how to ask your real question.
Your question boils down into two questions.
"How do I determine proper progression in my game via stats?" and "What stat spreads are important to the game I'm making?"
The problem is that those are really only things you can answer. Let me clarify.
Progression will be determined by planned length of game, planned stats (are you going to use higher or lower values?), and damage formulas. If your game is only a few hours long, progression won't be that useful, especially in terms of stats. If your game clocks in at 70 hours, then you're going to want to keep progression at least steady over those hours to ensure players don't suddenly start having issues with battles. If you plan on using higher level stats, then you can use more complex formulas for damage and points in each stat will actually mean a lot. If you plan on using lower level stats, then your damage formulas will be fairly simplistic and regular stat gain may not mean very much. If you want to use multiplicative damage formulas, then you'll have to consider slower progression so that these formulas do not unbalance your game. If you want to use additive formulas, then you'll have to consider a fairly quick progression as your stats likely won't mean a whole lot in terms of damage variation or growth.
As for your stat spreads and which are important... Well, that's largely based upon what kind of game you're designing. How valuable your stats are is determined by the formulas you'll be using to determine damage. Many designers think of the "Luck" stat as fairly useless. Well, if you only consider what it does by default to the VX Ace engine... then yeah, it's not that useful. It determines the chance a state will be inflicted (if I remember correctly). However, in the hands of someone with more imagination, it can be used as an attack stat or defense stat. It can be renamed and used in different formulas to be useful in its own way. Same with the AGL stat. It determines turn order. Okay, so what? Well, if you make as many skills that run off of it that run off of Magic or Attack skills, then it's suddenly fairly valuable as a stat.
Before you get into all the questions about "How long should it take to get stat progression?" and "how many xp points should I assign per level/monster?" you need to decide on what kind of game you want first. You cannot delve into your stats and battles unless you know exactly what you're aiming for in a game first.
Let me toot my own horn here for a minute and give you examples of what I'm doing. In my RPG, it takes a fairly long time to level up because I didn't really want players "grinding levels". I also disconnected stat gains from level ups to ensure that "grinding levels" wasn't the way your characters became more powerful. Instead, I use "level ups" as a means to get my players to explore the map each time they gain a level just to see what's changed. Gaining a level opens up shortcuts or sometimes adds new things to locations. Perhaps a ladder appears to let you take a shortcut up the mountain. Maybe some debris vanishes to let you through on a road. I use level ups as a means to get players to explore the map again and again. To tread the same ground, but still feel the delight of "exploring a new place". Likewise, I linked stat gains to only items. Items I only give out upon the completion of Quests. I wanted players to engage in the narrative and not care so much about grinding for xp or money. I wanted them to get engaged in the characters, the places, the lore, the backstories, and the events going on around them. These items that give stats can be used on anyone so that a player can distribute stats however they want amongst their party. Likewise, I keep stats fairly low in order to keep the nightmare of battle balancing under control. 20 HP to start with doesn't seem like much, but if it still takes 10 hits to kill you from basic enemies, it's a decent amount of HP. 20 MP doesn't seem like much until you realize that most basic spells are cast for 1-3 MP. 10 Defense doesn't seem like much, but if the enemy only has 10 Attack to throw at you, you don't take any damage at all. I also made my "small stats" matter by changing many of the formulas. Attack/Defense pairing, Magic/Magic Defense pairing, and Speed/Luck pairing. I gave each character a specialization in one of those three pairings so that they'd have an initial stat that would actually matter to the player. Enemies with low Luck attributes (or player characters) would take a lot of damage to skills that used Speed in their formula. Equipment in the game also gives the same fairly small stat bonuses that using those items gives. The starting equipment generally only gives one or two points. Some of the more expensive starting gear can give as many as ten.
It's about knowing what kind of game you want to make and how to set about doing that with your stats. What do you want players to be doing? Do you want them to know how the formulas for your skills work? Do you want to lessen the workload on yourself? Do you want to make intricate formulas to keep players guessing just how the heck their damage is calculated based on their stats? You need to decide on what kind of game you're making to decide how you want stat progression and balancing to work.
Build the stuff you enjoy building, and as you get closer to being able to call it a genuine game, find someone who's good at building up the RPG mechanics and have them help you out!
