As a general rule the more letters of RETAINS you have, the greater the chance of a bonus. 

Below are all the bonus words you can make if you have six of those letters, TISANE, and one other letter.

There are a lot of words, so to make learning easier, perhaps break them down into groups of 10-15 words or by distinct letter groups (i.e TISANE+A, B, C, D and E).

TISANE + 

A - ENTASIA, TAENIAS

B - BANTIES, BASINET, BESAINT, BESTAIN

C - ACETINS, CANIEST, CINEAST

D - DESTAIN, DETAINS, INSTEAD, NIDATES, SAINTED, SATINED, STAINED

E - ETESIAN

F - FAINEST, FANSITE, NAIFEST

G - EASTING, EATINGS, GAINEST, GENISTA, INGATES, INGESTA, SEATING, TAGINES, TANGIES, TEASING, TSIGANE

H - SHEITAN, STHENIA

I - ISATINE

J - JANTIES, TAJINES

K - INTAKES, KENTIAS, TANKIES

L - EASTLIN, ELASTIN, ENTAILS, NAILSET, SALIENT, SALTINE, SLAINTE, STANIEL, TENAILS

M - ETAMINS, INMATES, MAINEST, MANTIES, TAMEINS, TAMINES

N - INANEST, NANITES, STANINE, TANNIES

O - ATONIES

P - PANTIES, PATINES, SAPIENT, SPINATE

Q - nothing

R - ANESTRI, ANTSIER, NASTIER, RATINES, RESIANT, RETAINS, RETINAS, RETSINA, STAINER, STARNIE, STEARIN

S - ENTASIS, NASTIES, SEITANS, SESTINA, TANSIES, TISANES

T - INSTATE, SATINET, TANTIES

U - AUNTIES. SINUATE

V - NAIVEST, NATIVES, VAINEST

W - AWNIEST, TAWNIES, WANIEST, WANTIES

X  - ANTISEX, SEXTAIN

Y - nothing

Z - ZANIEST, ZEATINS 

96 words in total. 2 letters TISANE doesn't combine with to make a bonus (Q, Y)