I small problem when I try to create beats

There are two types of patterns: Audio Loops and Synth Sequences. Audio Loops consist of a digital audio recording of something and you don't need anything else to play them. Synth Sequences consist of a series of MIDI messages which specify which notes to play - they are more like a small score instead of an audio recording. In order to play a sequence you must also select which instrument sound (Patch) will play it. To do this, just select a suitable Patch for the same part playing the sequence.

This also means that even if the Patterns are classified as "Bass", "Leads", etc, this isn't actually the type of sound you will hear (except for audio loops). For example, you can play one of the Bass patterns with an Electric Piano sound, etc. Furthermore, you can modify the sounds you use as the sequence plays.

Exactly. You can play the synthesizers with a MIDI keyboard. As for specific models, I think the cheapest are the Evolution range - the price will depend on how many octaves and knobs but I think you can get the smallest keyboard (the MK225C) for about $100. I have one of those and it works well with Kinetic.