i use nsi products and the french fin tips are not meant to be blended.
you apply the tips and then apply white l&p liquid and powder (acrylic) over the top of the tip and then apply pink or clear to zones 2&3. these are used to help you with your smile lines.
i would also recommend to use natural tips but you can only use what you have been taught and while i agree that cnd performance tips are great as they do not need blending they are not suitible for everyones nails and there for you would need other natural tips that require blending which i do not think you should do untill you have been taught as you can cause damage to your clients nails if they are not blended correctly.
i hope i havent got the wrong end of the stick here so please correct me if i have.
i hope this helps.