What to look for in bits?

[CrazeUK]

Hi Guys.

So i am new to the whole CNC thing.

Over the past few weeks i have purchased a whole load of bits from eBay to get me going.
I have a range of bits with 2 flutes and 4 flutes in various lengths. So far all have been end mill with a few that are Vcarve 60degrees.

Depending on the materials, these are the parameters:
Feed: I have slowed the machine right down to between 5mm/sec to 20mm/sec.
RPM: Using a Kress settings 1-6 (6k - 25k)
I know for the different materials you need to cut at different RPM's and different feed rates.
Clamping: Using Clamps to hold down in addition to double sided sign tape.
Passes: I know to make less work on Lucy machine i am doing multiple passes on most materials, only cutting a max of up-to 3mm a time.

I aim to mainly cut:
Foam board (upto 19mm)
Dibond (probably upto 5mm)
Acrylic (Upto 12mm)
MDF (upto 12mm)
Other woods (uknown as yet).

I have been having quite a few issues with my machine over the past week (call it teething problems). I know initially i was feeding too high, which i have knocked right back.

1. Acrylic / Dibond Rough edges
2. Head jumping and losing steps
3. The Z axis 'appears' to slip down.
5. The cut going off track
6. Missing steps.
7. Acrylic melting the cuts together.

So i have some questions which may help the situation:
1. Do the number of flutes matter?
2. Does the quality of bit make a big difference (most currently from chin probably).
3. Are there recommended rules of thumb rates for feed / rpm. I know there are really complex calculators for them.
4. Anything else that may help?

Thanks in advance.

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Machine stats:
Just as a reminder,
I have a 1m x 1m,
Dimension: 3 + 1 (mirrored)
Drive type: Belt
X / y Axis frame: 20x80mm V Slot