The basic reason for using a parallel tuned circuit as the exciter is one of efficiency. If your inductor and tuned capacitor are 33uH and 75nF, resonant frequency will be about 101kHz. If you do the math you'll see that a lossless tuned circuit like this exhibits infinite impedance but still circulates high current between cap and inductor.
Lossless circuit are of course impossible but making the losses as low as possible means that if your inductance is 33uH and your applied voltage is (say) 40VRMS at 100kHz, the current in the inductor is: -
\$\dfrac{40V}{2\cdot\pi\cdot F\cdot L}\$ = 1.93 Amps
Your H bridge won't even be breaking into a sweat because it won't be supplying anything like this current. This current is due to the voltage across the inductor but the capacitor has the effect of performing "power-factor" correction and because the losses are low maybe the H bridge will be supplying in the order of 50mA to a couple of hundred mA.
However, your H bridge is exciting the coil/cap with a square wave and there will be losses due to the harmonics within the square wave. Because of this it makes sense to feed the coil/cap via an inductor too - somewhat smaller than the coil (maybe 1 quarter). You will also need to retune the capacitance to compensate for this. Some experimentation in this is required to get best results but, you should aim to reduce the H bridge's current to avoid it overheating.
I'd also say make one larger coil suitable for all three inductive loads. The larger coil can be any regular shape that suits your requirements for placement of the receiving coils.
Optimum performance is when the receiving coils are also tuned with a capacitor but, because the induced voltage is in series with a receive coil, the tuned circuit behaves like a series tuned circuit and, if the coupling is too great it will heavily detune the transmit coil when it is close by. You should aim for a minimum gap or incorporate circuits in the H bridge that current limit.
I strongly advise you to use something like LTSpice for simulating this - you'll learn a lot about the various interactions. I'd also recommend you read a bit about tesla coils because that is what are are intending to build (when tuned as per my thoughts).
Should i buy it instead of using winding inductor
Probably not if it's intended as the resonating coil in a 100MHz FM transmitter. Chances are this inductor will have a self-resonant-frequency below your transmission frequency and then it will behave like a capacitor. Also there are the inductor's losses to consider - basically you need a fairly high Q at your operating frequency but the small ferrite the inductor may be wound on may have high losses over (say) 500kHz.
If you are using the inductor at non-critical frequencies in non-critical areas of the circuit then maybe it'll be OK. My advice as usual on these type of questions, read the data sheet and understand that the inductor has self-resonance due to interwinding capacitance and losses that may rise exponentially with frequency.
Best Answer
Inductance
Inductance is proportional to turns squared, all things being equal.
L2 / L1 = N2^2 / N1^2 ... 1 so
N2^2 = N1^2 x (L2/l1) ... 2 so
N2 = N1 x sqrt (L2/L1) .... 3
Apply 3. above
For 15 uH:
L1 = 22 uH
L2 = 15 uH
N1 = 50 so
N2 = 50 x sqrt(15/22) = 50 x 0.826 =~ 41.3 turns
So 41 turns in theory and maybe 40 - 42 range.
Similarly for 7 uH N = 50 x sqrt(7/22) =~ 28turns
Current rating:
Core magnetisation depends on "ampere-turns" so current handling capacity will increase with the inverse of the turns ratios.
I2 = I1 x N1/N2
So 15 uH & 41 turns will handle
9A x 50/41 =~~~= 11A
...
Thicker wire may be required depending on actual currents used, as copper losses increase with I^2.
Treat all such results with care and test in practice.
Insulation:
You do not describe the core type or former used.
You say 500V rating - I don't know what voltage you are using in practice but, be sure that insulation is (more than) adequate for the task. As you intend to use existing windings, take care not to nick insulation or have wire rub against core edge. If a bobbin former or insulated core is used this should be easy enough to manage. Odds are a 500-V rated part does not use a bare core and depend on wire insulation alone :-)