I do not think there is a way to get both air and electric blast and also expand into two other elements, sorry.
Is one of them something you could replace with a blast from a second element (e.g. do you want electric just for a touch attack)? What specifically are you trying to do?
One thing I would suggest- don't worry too much about composite blasts. Except for Gathlain Kineticists, composite blasts are a very late game consideration- you cannot do them at all until level 7, and you cannot use them with impunity (i.e. without burn or risking the full round gather power) until you get supercharge at level 11.
If your first two elements do not combine nicely, you can always just rely on the empower metakinesis- it's 150% damage instead of 200%, but it's also doable for 0 burn from the onset.
I feel like, when picking elements, the thing to focus on are infusions/utility talents.
What are your other two elements? If it's like water+earth, you could pick electric blast at level 1 and then water at level 7 so you can use the charged water and mud composites.
then is there an item that can boost my to hit other then a dex belt?
A 4000 gp cracked pale green prism ioun stone gets you a +1 competence bonus, and taking an wysp familiar with greater elemental whispers can give you +5 to hit with aid another. Keep your elemental overflow capped (invest burn into a good defense at breakfast) and you're essentially full BAB.
how is it granting a +5 to aid another btw?
Wysp familiars-
Resonance (Ex)
A wysp’s natural resonance strengthens the power of its element. The wysp grants a +2 competence bonus on attack rolls and damage rolls to all creatures within 30 feet with an elemental subtype that matches the wysp’s, and to the DCs of all racial spell-like, supernatural, and extraordinary abilities of such creatures (as usual, this does not include creatures assuming an elemental form).Kineticists within 30 feet who share the wysp’s element gain a +1 competence bonus on attack rolls and damage rolls. The wysp’s statistics already include these bonuses.
Servitor (Ex)
A wysp is a natural servitor. When it uses the aid another action to assist a creature benefiting from its resonance, the wisp can grant that creature a +4 bonus instead of +2. No other effect can increase this bonus beyond +4.
So you pick up an air wysp or an aether wysp with the greater elemental whispers talent, it gives you +1 to hit and damage with all of your attacks, but if you delay in the turn order until after your familiar you get an extra +4 to hit. If you can't make the aid another thing work, take the Emissary familiar archetype so your familiar casts guidance on you on its turn, every turn for a total of +2 to hit.
and what does it mean by not getting the familiar benefits with greater element wispers
Normal Familiars grant special bonuses depending on the type of familiar. For example, a cat grants a bonus to stealth, while a rabbit grants a bonus to initiative.
Since Greater Whispers trades out your previous familiar, you don't get to keep its unique familiar bonus.
Can't say I know of a way to get a Familiar bonus back.
A Greater Elemental Whispers familiar also differs from a normal familiar in that it has half of your HP, which is a lot more HP than a Wizard's got. So at high levels the familiar may have more HP than some of your party members.
Yeah, but half a kineticist's HP is generally a lot more than half a wizard's HP, and the familiar doesn't take burn.
A high level Kineticist can invest a truly staggering amount of resources into their HP (it only takes 3 days to retrain an HD), so something like 400+ at level 18 is not inconceivable.
A familiar uses your BAB, the base save bonuses of yourself or the base familiar (whichever is higher for each save), your skill ranks or its own (whichever's higher), and gets intelligence and natural armor bonuses as per the table you'll see under the wizard. It also gets some other abilities like share spells from the same table.
Edit: and it gets half its masters HP as you know already.
A high level Kineticist can invest a truly staggering amount of resources into their HP (it only takes 3 days to retrain an HD), so something like 400+ at level 18 is not inconceivable.
I'm only speaking for myself here but I've never known a GM to allow that, in fact I've never even known a player to ask.
If there is one thing I would never recommend other players do it's things that could come across as rules cheesy.
would I keep all its ability scores the same? and if the base creature has a higher int would its int stay higher?
For reasons I don't understand the official ruling is that the Int gets replaced whether or not it's higher. Ask your GM to change it if that annoys you as much as it does me. The other ability scores will stay the same.